dt-bindings: display: add google, cros-ec-anx7688.yaml

ChromeOS EC ANX7688 is a display bridge that converts HDMI 2.0 to
DisplayPort 1.3 Ultra-HDi (4096x2160p60). It is an Analogix ANX7688 chip
which is connected to and operated by the ChromeOS Embedded Controller
(See google,cros-ec.yaml). It is accessed using I2C tunneling through
the EC and therefore its node should be a child of an EC I2C tunnel node
(See google,cros-ec-i2c-tunnel.yaml).

ChromOS EC ANX7688 is found on Acer Chromebook R13 (elm)
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210518141927.24795-2-dafna.hirschfeld@collabora.com

Documentation/devicetree/bindings/display/bridge/google,cros-ec-anx7688.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/google,cros-ec-anx7688.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ChromeOS EC ANX7688 HDMI to DP Converter through Type-C Port
+
+maintainers:
+  - Nicolas Boichat <drinkcat@chromium.org>
+  - Enric Balletbo i Serra <enric.balletbo@collabora.com>
+
+description: |
+  ChromeOS EC ANX7688 is a display bridge that converts HDMI 2.0 to
+  DisplayPort 1.3 Ultra-HDi (4096x2160p60). It is an Analogix ANX7688 chip
+  which is connected to and operated by the ChromeOS Embedded Controller
+  (See google,cros-ec.yaml). It is accessed using I2C tunneling through
+  the EC and therefore its node should be a child of an EC I2C tunnel node
+  (See google,cros-ec-i2c-tunnel.yaml).
+
+properties:
+  compatible:
+    const: google,cros-ec-anx7688
+
+  reg:
+    maxItems: 1
+    description: I2C address of the device.
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Video port for HDMI input.
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: USB Type-c connector.
+
+    required:
+      - port@0
+      - port@1
+
+required:
+  - compatible
+  - reg
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    i2c_tunnel_b: i2c-tunnel1 {
+        compatible = "google,cros-ec-i2c-tunnel";
+        google,remote-bus = <1>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        anx7688: anx7688@2c {
+            compatible = "google,cros-ec-anx7688";
+            reg = <0x2c>;
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+                port@0 {
+                    reg = <0>;
+                    anx7688_in: endpoint {
+                        remote-endpoint = <&hdmi0_out>;
+                    };
+                };
+                port@1 {
+                    reg = <1>;
+                    anx7688_out: endpoint {
+                        remote-endpoint = <&typec_connector>;
+                    };
+                };
+            };
+        };
+    };
+