dt-bindings: display: Add ingenic,ipu.yaml

Add documentation of the Device Tree bindings for the Image Processing
Unit (IPU) found in most Ingenic SoCs.

v2: Add missing 'const' in items list
v3: No change
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200716163846.174790-3-paul@crapouillou.net

Documentation/devicetree/bindings/display/ingenic,ipu.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/ingenic,ipu.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Ingenic SoCs Image Processing Unit (IPU) devicetree bindings
+
+maintainers:
+  - Paul Cercueil <paul@crapouillou.net>
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+        - ingenic,jz4725b-ipu
+        - ingenic,jz4760-ipu
+      - items:
+        - const: ingenic,jz4770-ipu
+        - const: ingenic,jz4760-ipu
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    const: ipu
+
+patternProperties:
+  "^ports?$":
+    description: OF graph bindings (specified in bindings/graph.txt).
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-names
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/jz4770-cgu.h>
+    ipu@13080000 {
+      compatible = "ingenic,jz4770-ipu", "ingenic,jz4760-ipu";
+      reg = <0x13080000 0x800>;
+
+      interrupt-parent = <&intc>;
+      interrupts = <29>;
+
+      clocks = <&cgu JZ4770_CLK_IPU>;
+      clock-names = "ipu";
+
+      port {
+        ipu_ep: endpoint {
+          remote-endpoint = <&lcdc_ep>;
+        };
+      };
+    };