[PATCH] dt-bindings: mailbox: xlnx,zynqmp-ipi-mailbox: Document msg region requirement

[Harini T]

Add description clarifying that for Versal IPI mailboxes, both host and
remote agents must have the "msg" register region defined for successful
message passing. Without both, only notification-based communication
works.

Signed-off-by: Harini T <harini.t at amd.com>
---
 .../bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml           | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml b/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
index 04d6473d666f..8fdf77c7935c 100644
--- a/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
+++ b/Documentation/devicetree/bindings/mailbox/xlnx,zynqmp-ipi-mailbox.yaml
@@ -165,6 +165,12 @@ allOf:
         reg-names: false
 
     else:
+      description:
+        For Versal IPI mailboxes, the "msg" register region is optional.
+        However, for successful message passing via mailbox, both the host IPI
+        agent and the remote IPI agent must have the "msg" register region
+        defined. If either agent lacks the "msg" field, only notification-based
+        communication (without message buffers) will work.
       properties:
         reg:
           items:
-- 
2.43.0