Bindings are added.  Only one interrupt is needed because
we do not yet employ the SCMI p2a channel.

Signed-off-by: Jim Quinlan <james.quinlan@broadcom.com>
---
 .../bindings/mailbox/brcm,brcmstb-mbox.yaml   | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mailbox/brcm,brcmstb-mbox.yaml

diff --git a/Documentation/devicetree/bindings/mailbox/brcm,brcmstb-mbox.yaml b/Documentation/devicetree/bindings/mailbox/brcm,brcmstb-mbox.yaml
new file mode 100644
index 000000000000..797c0cc609a3
--- /dev/null
+++ b/Documentation/devicetree/bindings/mailbox/brcm,brcmstb-mbox.yaml
@@ -0,0 +1,39 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+$id: http://devicetree.org/schemas/mailbox/brcm,brcmstb-mbox.yaml#
+
+title: Broadcom STB mailbox driver bindings
+
+maintainers:
+  - Jim Quinlan <james.quinlan@broadcom.com>
+
+properties:
+  compatible:
+    enum:
+      - brcm,brcmstb-mbox
+
+  interrupts:
+    items:
+      - description: a2p return interrupt, indicates SCMI msg completion.
+
+  "#mbox-cells":
+    const: 1
+
+required:
+  - compatible
+  - interrupts
+  - "#mbox-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+    mailbox {
+      compatible = "brcm,brcmstb-mailbox";
+      #mbox-cells = <1>;
+      interrupts = <GIC_SPI 0xc6 IRQ_TYPE_LEVEL_HIGH>;
+    };
+...
-- 
2.17.1