Appellants assert in their first proposition of law that the court of appeals erred in denying the writ of prohibition because the dismissal of the previous common pleas court action barred Ingle’s subsequent declaratory judgment action in probate court based on res judicata.
In order to be entitled to a writ of prohibition, appellants must establish (1) that the probate court and Judge Corrigan are about to exercise judicial or quasijudicial power, (2) that the exercise of that power is unauthorized by law, and (3) that denying the writ will result in injury for which no other adequate remedy exists in the ordinary course of law. State ex rel. Fowler v. Smith (1994), 68 Ohio St.3d 357, 359, 626 N.E.2d 950, 952. Here, it is uncontroverted that unless restrained, appellees will exercise judicial power in the declaratory judgment action brought by Ingle in her capacity as representative of the decedents’ estates.
As to the remaining elements that appellants had to prove in order to be entitled to a writ of prohibition, appellants’ main claim both below and on appeal is that res judicata divested the probate court of jurisdiction over the declaratory judgment action. Appellants contend that the dismissal of Ingle’s prior complaint following commencement of jury trial, appeal, and remand operated as an adjudication on the merits which barred the subsequent declaratory judgment action which involved the same parties and claims. See Civ.R. 41(A)(1) and *21(B)(3); see, also, State ex rel. Avellone v. Lake Cty. Bd. of Commrs. (1989), 60 Ohio App.3d 127, 574 N.E.2d 577.
Appellants’ contention is meritless because res judicata is an affirmative defense which does not divest the jurisdiction of the second tribunal to decide the validity of that defense. State ex rel. Flower v. Rocker (1977), 52 Ohio St.2d 160, 162, 6 O.O.3d 375, 376, 370 N.E.2d 479, 480 (writ of prohibition did not lie, since court had jurisdiction to rule on affirmative defense of res judicata); State ex rel. LTV Steel Co. v. Gwin (1992), 64 Ohio St.3d 245, 251, 594 N.E.2d 616, 621 (writ of prohibition denied where issue of res judicata did not attack appellate court’s jurisdiction); see, generally, 63A American Jurisprudence 2d (1984) 180, Prohibition, Section 48 (“The fact that the defense of res judicata based on a decision in a former action is available in a second action involving the same issues does not deprive the court in which the second action is brought of jurisdiction to try the case again, so as to warrant the issuance of a writ of prohibition to prevent such court from proceeding with the suit, and the only remedy of the aggrieved party is to set up the res judicata plea as a defense in that suit and to appeal from an adverse decision therein.”). In addition, this case does not involve the repeated and vexatious abuse of the judicial process which at times warrants the issuance of a writ of prohibition. See State ex rel. Stark v. Summit Cty. Court of Common Pleas (1987), 31 Ohio St.3d 324, 325, 31 OBR 599, 600, 511 N.E.2d 115, 117; State v. Steffen (1994), 70 Ohio St.3d 399, 408, 639 N.E.2d 67, 74.
In that appellees possess jurisdiction to decide appellants’ affirmative defense of res judicata and appellants have an adequate remedy by appeal to challenge any adverse decision, appellants are not entitled to a writ of prohibition based on this contention. In fact, when the court of appeals decided the issue, the probate court referee had merely recommended overruling a motion to dismiss filed by appellants in the declaratory judgment action based upon the same “jurisdictional” claim. There is no indication of any final judgment in the declaratory judgment action by appellees. Prohibition may not be employed as a substitute for appeal from an interlocutory order. State ex rel. Keenan v. Calabrese (1994), 69 Ohio St.3d 176, 178, 631 N.E.2d 119, 121. Appellants’ first proposition of law is overruled.
Appellants assert in their second proposition of law that the probate court and Judge Corrigan do not have jurisdiction over the declaratory judgment action because it is in reality an action for wrongful conversion of assets filed by a personal representative of the deceased owner of the assets where the owner unconditionally and validly completed the transfer of the funds to the transferee.
Although appellants did not raise this claim in the court of appeals or in the declaratory judgment action, it is not waived on appeal because it is not completely inconsistent with the general argument below that the probate court *22lacks jurisdiction, see State ex rel. Jones v. Hendon (1993), 66 Ohio St.3d 115, 118, 609 N.E.2d 541, 543, fn. 2, and the issue of a court’s subject-matter jurisdiction cannot be waived. State v. Wilson (1995), 73 Ohio St.3d 40, 46, 652 N.E.2d 196, 200.
A writ of prohibition will issue where there is a patent and unambiguous restriction on the jurisdiction of the court which clearly places the dispute outside the court’s jurisdiction. State ex rel. Koren v. Grogan (1994), 68 Ohio St.3d 590, 593, 629 N.E.2d 446, 449. Absent a patent and unambiguous lack of jurisdiction, a court having general subject-matter jurisdiction can determine its own jurisdiction, and a party .challenging the court’s jurisdiction has an adequate remedy by way of appeal. State ex rel. Enyart v. O’Neill (1995), 71 Ohio St.3d 655, 656, 646 N.E.2d 1110, 1112.
Since the probate court is a court of limited jurisdiction, probate proceedings are restricted to those actions permitted by statute and by the Constitution. Corron v. Corron (1988), 40 Ohio St.3d 75, 531 N.E.2d 708, paragraph one of the syllabus. R.C. 2101.24(A)(1)(k), 2721.03, and 2721.05(C) vest probate courts with jurisdiction over declaratory judgment actions upon questions relating to the administration of an estate. Zuendel v. Zuendel (1992), 63 Ohio St.3d 733, 735-736, 590 N.E.2d 1260, 1262; see Wozniak v. Wozniak (1993), 90 Ohio App.3d 400, 407-408, 629 N.E.2d 500, 505. It has been held that a declaratory judgment action may be brought in the probate court to determine the validity of inter vivos transfers where the property transferred would revert to the estate if the transfers are. invalidated. Bobko v. Sagen (1989), 61 Ohio App.3d 397, 406-407, 572 N.E.2d 823, 829; see, also, Corron, supra, 40 Ohio St.3d at 79, 531 N.E.2d at 712; Carlin v. Mambuca (1994), 96 Ohio App.3d 500, 505, 645 N.E.2d 737, 740; Eger v. Eger (1974), 39 Ohio App.2d 14, 18, 68 O.O.2d 150, 153, 314 N.E.2d 394, 400. We agree.
The allegations of the complaint for declaratory judgment filed by Ingle, in her capacities as executor and administrator of the decedents’ estates, are of sufficient breadth so that appellees do not patently and unambiguously lack jurisdiction. See, also, State ex rel. Lewis v. Moser (1995), 72 Ohio St.3d 25, 647 N.E.2d 155. As in Bobko, Ingle claims that the inter vivos transfers were ineffective and that the transferred assets were the property of the decedents’ estates. Like State ex rel. Fenwick v. Finkbeiner (1995), 72 Ohio St.3d 457, 459-460, 650 N.E.2d 896, 898, appellees have at least basic authority to proceed in the declaratory judgment action.
The court of appeals did not err in relying on Bobko to hold that the probate court and Judge Corrigan did not patently and unambiguously lack jurisdiction and that appellants had an adequate remedy by appeal to raise the jurisdictional issue. Appellants failed to establish entitlement to extraordinary relief in prohi*23bition. Accordingly, appellants’ second proposition of law is overruled, and the judgment of the court of appeals is affirmed.
Judgment affirmed.
Moyer, C.J., Douglas, Wright, Resnick, F.E. Sweeney, Pfeifer and Cook, JJ., concur.