dt-bindings: display: renesas,du: Document cmms property

Document the newly added 'renesas,cmms' property which accepts a list of
phandle and channel index pairs that point to the CMM units available
for each Display Unit output video channel.
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>

Documentation/devicetree/bindings/display/renesas,du.txt

@@ -46,6 +46,10 @@ Required Properties:
     instance that serves the DU channel, and the channel index identifies the
     LIF instance in that VSP.
 
+  - renesas,cmms: A list of phandles to the CMM instances present in the SoC,
+    one for each available DU channel. The property shall not be specified for
+    SoCs that do not provide any CMM (such as V3M and V3H).
+
 Required nodes:
 
 The connections to the DU output video ports are modeled using the OF graph
@@ -93,6 +97,7 @@ Example: R8A7795 (R-Car H3) ES2.0 DU
 			 <&cpg CPG_MOD 721>;
 		clock-names = "du.0", "du.1", "du.2", "du.3";
 		vsps = <&vspd0 0>, <&vspd1 0>, <&vspd2 0>, <&vspd0 1>;
+		renesas,cmms = <&cmm0>, <&cmm1>, <&cmm2>, <&cmm3>;
 
 		ports {
 			#address-cells = <1>;