dt-bindings: display: bridge: ldb: Implement simple Freescale i.MX8MP LDB bridge

The i.MX8MP contains two syscon registers which are responsible
for configuring the on-SoC DPI-to-LVDS serializer. Add DT binding
which represents this serializer as a bridge.
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Maxime Ripard <maxime@cerno.tech>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Robby Cai <robby.cai@nxp.com>
Cc: Robert Foss <robert.foss@linaro.org>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: devicetree@vger.kernel.org
To: dri-devel@lists.freedesktop.org
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220426193645.244792-1-marex@denx.de

Documentation/devicetree/bindings/display/bridge/fsl,ldb.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/bridge/fsl,ldb.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Freescale i.MX8MP DPI to LVDS bridge chip
+
+maintainers:
+  - Marek Vasut <marex@denx.de>
+
+description: |
+  The i.MX8MP mediamix contains two registers which are responsible
+  for configuring the on-SoC DPI-to-LVDS serializer. This describes
+  those registers as bridge within the DT.
+
+properties:
+  compatible:
+    const: fsl,imx8mp-ldb
+
+  clocks:
+    maxItems: 1
+
+  clock-names:
+    const: ldb
+
+  ports:
+    $ref: /schemas/graph.yaml#/properties/ports
+
+    properties:
+      port@0:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Video port for DPI input.
+
+      port@1:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Video port for LVDS Channel-A output (panel or bridge).
+
+      port@2:
+        $ref: /schemas/graph.yaml#/properties/port
+        description: Video port for LVDS Channel-B output (panel or bridge).
+
+    required:
+      - port@0
+      - port@1
+
+required:
+  - compatible
+  - clocks
+  - ports
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/imx8mp-clock.h>
+
+    blk-ctrl {
+        bridge {
+            compatible = "fsl,imx8mp-ldb";
+            clocks = <&clk IMX8MP_CLK_MEDIA_LDB>;
+            clock-names = "ldb";
+
+            ports {
+                #address-cells = <1>;
+                #size-cells = <0>;
+
+                port@0 {
+                    reg = <0>;
+
+                    ldb_from_lcdif2: endpoint {
+                        remote-endpoint = <&lcdif2_to_ldb>;
+                    };
+                };
+
+                port@1 {
+                    reg = <1>;
+
+                    ldb_lvds_ch0: endpoint {
+                        remote-endpoint = <&ldb_to_lvdsx4panel>;
+                    };
+                };
+
+                port@2 {
+                    reg = <2>;
+
+                    ldb_lvds_ch1: endpoint {
+                    };
+                };
+            };
+        };
+    };