dt-bindings: serial: document esp32-uart

Add documentation for the ESP32xx UART controllers.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20231010085926.1021667-3-jcmvbkbc@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/devicetree/bindings/serial/esp,esp32-uart.yaml

+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/serial/esp,esp32-uart.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ESP32xx UART controllers
+
+maintainers:
+  - Max Filippov <jcmvbkbc@gmail.com>
+
+description:
+  ESP32 UART controller is a part of the ESP32 SoC.
+  ESP32S3 UART controller is a part of the ESP32S3 SoC.
+  Both SoCs are produced by Espressif Systems Co. Ltd.
+
+allOf:
+  - $ref: serial.yaml#
+
+properties:
+  compatible:
+    enum:
+      - esp,esp32-uart
+      - esp,esp32s3-uart
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    serial@60000000 {
+      compatible = "esp,esp32s3-uart";
+      reg = <0x60000000 0x80>;
+      interrupts = <27 1 0>;
+      clocks = <&serial_clk>;
+    };