spi: dt-bindings: add loongson spi

Add the Loongson platform spi binding with DT schema format using
json-schema.

Signed-off-by: Yinbo Zhu <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

Documentation/devicetree/bindings/spi/loongson,ls2k-spi.yaml

···
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/spi/loongson,ls2k-spi.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Loongson SPI controller
+
+maintainers:
+  - Yinbo Zhu <[e-mail]>
+
+allOf:
+  - $ref: /schemas/spi/spi-controller.yaml#
+
+properties:
+  compatible:
+    oneOf:
+      - enum:
+          - loongson,ls2k1000-spi
+      - items:
+          - enum:
+              - loongson,ls2k0500-spi
+          - const: loongson,ls2k1000-spi
+
+  reg:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - clocks
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    spi0: spi@1fff0220{
+        compatible = "loongson,ls2k1000-spi";
+        reg = <0x1fff0220 0x10>;
+        clocks = <&clk 17>;
+        #address-cells = <1>;
+        #size-cells = <0>;
+    };

MAINTAINERS

···
 F:	drivers/clk/clk-loongson2.c
 F:	include/dt-bindings/clock/loongson,ls2k-clk.h
 
+LOONGSON SPI DRIVER
+M:	Yinbo Zhu <[e-mail]>
+L:	[e-mail]
+S:	Maintained
+F:	Documentation/devicetree/bindings/spi/loongson,ls2k-spi.yaml
+
 LOONGSON-2 SOC SERIES GUTS DRIVER
 M:	Yinbo Zhu <[e-mail]>
 L:	[e-mail]