dt-bindings: serial: add bindings doc for Bouffalolab uart driver

Add bindings doc for Bouffalolab UART Driver

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>

Documentation/devicetree/bindings/serial/bouffalolab,uart.yaml

@@ -0,0 +1,50 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2022 Jisheng Zhang <jszhang@kernel.org>
+%YAML 1.2
+---
+$id: "http://devicetree.org/schemas/serial/bouffalolab,uart.yaml#"
+$schema: "http://devicetree.org/meta-schemas/core.yaml#"
+
+title: Bouffalolab UART Controller
+
+maintainers:
+  - Jisheng Zhang <jszhang@kernel.org>
+
+allOf:
+  - $ref: serial.yaml#
+
+properties:
+  compatible:
+    const: bouffalolab,uart
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    aliases {
+        serial0 = &uart0;
+    };
+
+    uart0: serial@30002000 {
+        compatible = "bouffalolab,uart";
+        reg = <0x30002000 0x1000>;
+        interrupts = <53 IRQ_TYPE_LEVEL_HIGH>;
+        clocks = <&xtal>;
+    };
+...