media: dt-bindings: mediatek: Add phandle to mediatek,scp on MDP3 RDMA

The MDP3 RDMA needs to communicate with the SCP remote processor: allow
specifying a phandle to a SCP core.
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>

Documentation/devicetree/bindings/media/mediatek,mdp3-rdma.yaml

@@ -45,6 +45,14 @@ properties:
       include/dt-bindings/gce/<chip>-gce.h of each chips.
     $ref: /schemas/types.yaml#/definitions/uint32-array
 
+  mediatek,scp:
+    $ref: /schemas/types.yaml#/definitions/phandle
+    description:
+      Phandle to the System Control Processor (SCP) used for initializing
+      and stopping the MDP3, for sending frame data locations to the MDP3's
+      VPU and to install Inter-Processor Interrupt handlers to control
+      processing states.
+
   power-domains:
     maxItems: 1