dt-bindings: display: renesas,rzg2l-du: Document RZ/G2UL DU bindings

Document DU found in RZ/G2UL SoC. The DU block is identical to RZ/G2L
SoC, but has only DPI interface.

While at it, add missing required property port@1 for RZ/G2L and RZ/V2L
SoCs. Currently there is no user for the DPI interface and hence there
won't be any ABI breakage for adding port@1 as required property for
RZ/G2L and RZ/V2L SoCs.
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240822162320.5084-2-biju.das.jz@bp.renesas.com

Documentation/devicetree/bindings/display/renesas,rzg2l-du.yaml

@@ -18,6 +18,7 @@ properties:
   compatible:
     oneOf:
       - enum:
+          - renesas,r9a07g043u-du # RZ/G2UL
           - renesas,r9a07g044-du # RZ/G2{L,LC}
       - items:
           - enum:
@@ -60,9 +61,6 @@ properties:
         $ref: /schemas/graph.yaml#/properties/port
         unevaluatedProperties: false
 
-    required:
-      - port@0
-
     unevaluatedProperties: false
 
   renesas,vsps:
@@ -88,6 +86,34 @@ required:
 
 additionalProperties: false
 
+allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: renesas,r9a07g043u-du
+    then:
+      properties:
+        ports:
+          properties:
+            port@0:
+              description: DPI
+
+          required:
+            - port@0
+    else:
+      properties:
+        ports:
+          properties:
+            port@0:
+              description: DSI
+            port@1:
+              description: DPI
+
+          required:
+            - port@0
+            - port@1
+
 examples:
   # RZ/G2L DU
   - |