FROMLIST: dt-bindings: serial: Add Loongson UART controller

Add Loongson UART controller binding with DT schema format using
json-schema.

Signed-off-by: Haowei Zheng <[email protected]>

Link: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Kexy Biscuit <[email protected]>

Author: Haowei Zheng

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

@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/loongson,uart.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Loongson UART
+
+maintainers:
+  - Haowei Zheng <[email protected]>
+
+allOf:
+  - $ref: serial.yaml
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+          - loongson,ls7a-uart
+          - loongson,ls3a5000-uart
+          - loongson,ls2k2000-uart
+      - items:
+          - enum:
+              - loongson,ls2k1000-uart
+              - loongson,ls2k0500-uart
+          - const: loongson,ls7a-uart
+      - items:
+          - enum:
+              - loongson,ls2k1500-uart
+          - const: loongson,ls2k2000-uart
+      - items:
+          - enum:
+              - loongson,ls3a6000-uart
+          - const: loongson,ls3a5000-uart
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clock-frequency: true
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clock-frequency
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/clock/loongson,ls2k-clk.h>
+
+    serial@1fe20000 {
+        compatible = "loongson,ls2k1000-uart", "loongson,ls7a-uart";
+        reg = <0x1fe20000 0x10>;
+        clock-frequency = <125000000>;
+        interrupt-parent = <&liointc0>;
+        interrupts = <0x0 IRQ_TYPE_LEVEL_HIGH>;
+    };