dt-bindings: display: panel: document Synaptics TDDI panel

Document the Synaptics TDDI (Touch/Display Integration) panel hardware.
Along with the MIPI-DSI panel, these devices also have an in-built LED
backlight device and a touchscreen, all packed together in a single chip.

Also, add compatibles for supported panels - TD4101 and TD4300. Both
have the '-panel' suffix so as to remove any ambiguity between the panel
and touchscreen chips.

Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Signed-off-by: Kaustabh Chakraborty <[e-mail]>
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

Documentation/devicetree/bindings/display/panel/synaptics,td4300-panel.yaml

···
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/display/panel/synaptics,td4300-panel.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Synaptics TDDI Display Panel Controller
+
+maintainers:
+  - Kaustabh Chakraborty <[e-mail]>
+
+allOf:
+  - $ref: panel-common.yaml#
+
+properties:
+  compatible:
+    enum:
+      - syna,td4101-panel
+      - syna,td4300-panel
+
+  reg:
+    maxItems: 1
+
+  vio-supply:
+    description: core I/O voltage supply
+
+  vsn-supply:
+    description: negative voltage supply for analog circuits
+
+  vsp-supply:
+    description: positive voltage supply for analog circuits
+
+  backlight-gpios:
+    maxItems: 1
+    description: backlight enable GPIO
+
+  reset-gpios: true
+  width-mm: true
+  height-mm: true
+  panel-timing: true
+
+required:
+  - compatible
+  - reg
+  - width-mm
+  - height-mm
+  - panel-timing
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/gpio/gpio.h>
+
+    dsi {
+        #address-cells = <1>;
+        #size-cells = <0>;
+
+        panel@0 {
+            compatible = "syna,td4300-panel";
+            reg = <0>;
+
+            vio-supply = <&panel_vio_reg>;
+            vsn-supply = <&panel_vsn_reg>;
+            vsp-supply = <&panel_vsp_reg>;
+
+            backlight-gpios = <&gpd3 5 GPIO_ACTIVE_LOW>;
+            reset-gpios = <&gpd3 4 GPIO_ACTIVE_LOW>;
+
+            width-mm = <68>;
+            height-mm = <121>;
+
+            panel-timing {
+                clock-frequency = <144389520>;
+
+                hactive = <1080>;
+                hsync-len = <4>;
+                hfront-porch = <120>;
+                hback-porch = <32>;
+
+                vactive = <1920>;
+                vsync-len = <2>;
+                vfront-porch = <21>;
+                vback-porch = <4>;
+            };
+        };
+    };
+
+...