dt-bindings: gpio: Add devicetree binding for RDA Micro GPIO controller

Add YAML devicetree binding for RDA Micro GPIO controller.
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20191021064413.19840-2-manivannan.sadhasivam@linaro.orgSigned-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/gpio/gpio-rda.yaml

+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/gpio-rda.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: RDA Micro GPIO controller
+
+maintainers:
+  - Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
+
+properties:
+  compatible:
+    const: rda,8810pl-gpio
+
+  reg:
+    maxItems: 1
+
+  gpio-controller: true
+
+  "#gpio-cells":
+    const: 2
+
+  ngpios:
+    description:
+      Number of available gpios in a bank.
+    minimum: 1
+    maximum: 32
+
+  interrupt-controller: true
+
+  "#interrupt-cells":
+    const: 2
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - gpio-controller
+  - "#gpio-cells"
+  - ngpios
+  - interrupt-controller
+  - "#interrupt-cells"
+  - interrupts
+
+additionalProperties: false
+
+...