dt-bindings: display: xlnx: zynqmp-dpsub: Add OF graph ports

The DPSUB doesn't live in isolation, but is connected to the
programmable logic for live inputs and outputs, and also has a
DisplayPort output. Model all those using OF graph.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/display/xlnx/xlnx,zynqmp-dpsub.yaml

@@ -117,6 +117,45 @@ properties:
       - const: dp-phy0
       - const: dp-phy1
 
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+    description: |
+      Connections to the programmable logic and the DisplayPort PHYs. Each port
+      shall have a single endpoint.
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: The live video input from the programmable logic
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: The live graphics input from the programmable logic
+
+      port@2:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: The live audio input from the programmable logic
+
+      port@3:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: The blended video output to the programmable logic
+
+      port@4:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: The mixed audio output to the programmable logic
+
+      port@5:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: The DisplayPort output
+
+    required:
+      - port@0
+      - port@1
+      - port@2
+      - port@3
+      - port@4
+      - port@5
+
 required:
   - compatible
   - reg
@@ -130,6 +169,7 @@ required:
   - dma-names
   - phys
   - phy-names
+  - ports
 
 additionalProperties: false
 
@@ -164,6 +204,33 @@ examples:
                <&psgtr 0 PHY_TYPE_DP 1 3>;
 
         phy-names = "dp-phy0", "dp-phy1";
+
+        ports {
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            port@0 {
+                reg = <0>;
+            };
+            port@1 {
+                reg = <1>;
+            };
+            port@2 {
+                reg = <2>;
+            };
+            port@3 {
+                reg = <3>;
+            };
+            port@4 {
+                reg = <4>;
+            };
+            port@5 {
+                reg = <5>;
+                dpsub_dp_out: endpoint {
+                    remote-endpoint = <&dp_connector>;
+                };
+            };
+        };
     };
 
 ...