dt-bindings: display: panel: add common dual-link schema

Add schema with common properties shared among dual-link panel ICs.

Reviewed-by: Laurent Pinchart <[e-mail]>
Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

Documentation/devicetree/bindings/display/panel/panel-common-dual.yaml

···
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/panel/panel-common-dual.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Common Properties for Dual-Link Display Panels
+
+maintainers:
+  - Thierry Reding <[e-mail]>
+  - Laurent Pinchart <[e-mail]>
+
+description:
+  Properties common for Panel IC supporting dual link panels.  Devices might
+  support also single link.
+
+allOf:
+  - $ref: panel-common.yaml#
+
+properties:
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+    additionalProperties: false
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: First link
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Second link
+
+      "#address-cells": true
+      "#size-cells": true
+
+    required:
+      - port@0
+
+# Single-panel setups are still allowed.
+oneOf:
+  - required:
+      - ports
+  - required:
+      - port
+
+additionalProperties: true