diff --git a/dts/bindings/ipm/st,stm32-hsem-mailbox.yaml b/dts/bindings/ipm/st,stm32-hsem-mailbox.yaml
index 813ca865f97..c8df24f2572 100644
--- a/dts/bindings/ipm/st,stm32-hsem-mailbox.yaml
+++ b/dts/bindings/ipm/st,stm32-hsem-mailbox.yaml
@@ -13,3 +13,11 @@ properties:
 
   interrupts:
     required: true
+
+  "#mbox-cells":
+    type: int
+    description: |
+      Dummy property for device tree compatibility with MBOX driver.
+
+mbox-cells:
+  - channel