dt-bindings: i3c: Add mctp-controller property

This property is used to describe a I3C bus with attached MCTP I3C
target devices.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Documentation/devicetree/bindings/i3c/i3c.yaml

@@ -55,6 +55,12 @@ properties:
 
       May not be supported by all controllers.
 
+  mctp-controller:
+    type: boolean
+    description: |
+      Indicates that the system is accessible via this bus as an endpoint for
+      MCTP over I3C transport.
+
 required:
   - "#address-cells"
   - "#size-cells"