dt-bindings: display: bridge: Add documentation for LT8912B

Lontium LT8912B is a DSI to HDMI bridge.

Signed-off-by: Adrien Grassein <adrien.grassein@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210326121955.1266230-2-adrien.grassein@gmail.com

Documentation/devicetree/bindings/display/bridge/lontium,lt8912b.yaml

@@ -0,0 +1,102 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/lontium,lt8912b.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Lontium LT8912B MIPI to HDMI Bridge
+
+maintainers:
+  - Adrien Grassein <adrien.grassein@gmail.com>
+
+description: |
+  The LT8912B is a bridge device which convert DSI to HDMI
+
+properties:
+  compatible:
+    enum:
+      - lontium,lt8912b
+
+  reg:
+    maxItems: 1
+
+  reset-gpios:
+    maxItems: 1
+    description: GPIO connected to active high RESET pin.
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description:
+          Primary MIPI port for MIPI input
+
+        properties:
+          endpoint:
+            $ref: /schemas/media/video-interfaces.yaml#
+            unevaluatedProperties: false
+
+            properties:
+              data-lanes: true
+
+            required:
+              - data-lanes
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: |
+          HDMI port, should be connected to a node compatible with the
+          hdmi-connector binding.
+
+    required:
+      - port@0
+      - port@1
+
+required:
+  - compatible
+  - reg
+  - reset-gpios
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    i2c4 {
+      #address-cells = <1>;
+      #size-cells = <0>;
+
+      hdmi-bridge@48 {
+        compatible = "lontium,lt8912b";
+        reg = <0x48>;
+        reset-gpios = <&max7323 0 GPIO_ACTIVE_LOW>;
+
+        ports {
+          #address-cells = <1>;
+          #size-cells = <0>;
+
+          port@0 {
+            reg = <0>;
+
+            hdmi_out_in: endpoint {
+              data-lanes = <0 1 2 3>;
+              remote-endpoint = <&mipi_dsi_out>;
+            };
+          };
+
+          port@1 {
+              reg = <1>;
+
+              endpoint {
+                  remote-endpoint = <&hdmi_in>;
+              };
+          };
+        };
+      };
+    };
+
+...