dt-bindings: Add binding for IT6505.

Add a DT binding documentation for IT6505.
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Allen Chen <allen.chen@ite.com.tw>
Signed-off-by: Pi-Hsun Shih <pihsun@chromium.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
[fixed example to use i2c]
Link: https://patchwork.freedesktop.org/patch/msgid/1587979103-5630-3-git-send-email-allen.chen@ite.com.tw

Documentation/devicetree/bindings/display/bridge/ite,it6505.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/ite,it6505.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ITE it6505 Device Tree Bindings
+
+maintainers:
+  - Allen Chen <allen.chen@ite.com.tw>
+
+description: |
+  The IT6505 is a high-performance DisplayPort 1.1a transmitter,
+  fully compliant with DisplayPort 1.1a, HDCP 1.3 specifications.
+  The IT6505 supports color depth of up to 36 bits (12 bits/color)
+  and ensures robust transmission of high-quality uncompressed video
+  content, along with uncompressed and compressed digital audio content.
+
+  Aside from the various video output formats supported, the IT6505
+  also encodes and transmits up to 8 channels of I2S digital audio,
+  with sampling rate up to 192kHz and sample size up to 24 bits.
+  In addition, an S/PDIF input port takes in compressed audio of up to
+  192kHz frame rate.
+
+  Each IT6505 chip comes preprogrammed with an unique HDCP key,
+  in compliance with the HDCP 1.3 standard so as to provide secure
+  transmission of high-definition content. Users of the IT6505 need not
+  purchase any HDCP keys or ROMs.
+
+properties:
+  compatible:
+    const: ite,it6505
+
+  ovdd-supply:
+    maxItems: 1
+    description: I/O voltage
+
+  pwr18-supply:
+    maxItems: 1
+    description: core voltage
+
+  interrupts:
+    maxItems: 1
+    description: interrupt specifier of INT pin
+
+  reset-gpios:
+    maxItems: 1
+    description: gpio specifier of RESET pin
+
+  extcon:
+    maxItems: 1
+    description: extcon specifier for the Power Delivery
+
+  port:
+    type: object
+    description: A port node pointing to DPI host port node
+
+required:
+  - compatible
+  - ovdd-supply
+  - pwr18-supply
+  - interrupts
+  - reset-gpios
+  - extcon
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    i2c {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        dp-bridge@5c {
+            compatible = "ite,it6505";
+            interrupts = <152 IRQ_TYPE_EDGE_FALLING 152 0>;
+            reg = <0x5c>;
+            pinctrl-names = "default";
+            pinctrl-0 = <&it6505_pins>;
+            ovdd-supply = <&mt6358_vsim1_reg>;
+            pwr18-supply = <&it6505_pp18_reg>;
+            reset-gpios = <&pio 179 1>;
+            extcon = <&usbc_extcon>;
+
+            port {
+                it6505_in: endpoint {
+                    remote-endpoint = <&dpi_out>;
+                };
+            };
+        };
+    };