dt-bindings: arm: Convert sprd board/soc bindings to json-schema

Convert Unisoc (formerly Spreadtrum) SoC bindings to DT schema format
using json-schema.
Signed-off-by: Chunyan Zhang <chunyan.zhang@unisoc.com>
[robh: dual license GPL/BSD]
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/sprd.txt

-Spreadtrum SoC Platforms Device Tree Bindings
-----------------------------------------------------
-
-SC9836 openphone Board
-Required root node properties:
-	- compatible = "sprd,sc9836-openphone", "sprd,sc9836";
-
-SC9860 SoC
-Required root node properties:
-	- compatible = "sprd,sc9860"
-
-SP9860G 3GFHD Board
-Required root node properties:
-	- compatible = "sprd,sp9860g-1h10", "sprd,sc9860";

Documentation/devicetree/bindings/arm/sprd.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright 2019 Unisoc Inc.
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/sprd.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Unisoc platforms device tree bindings
+
+maintainers:
+  - Orson Zhai <orsonzhai@gmail.com>
+  - Baolin Wang <baolin.wang7@gmail.com>
+  - Chunyan Zhang <zhang.lyra@gmail.com>
+
+properties:
+  $nodename:
+    const: '/'
+  compatible:
+    oneOf:
+      - items:
+          - enum:
+              - sprd,sc9836-openphone
+          - const: sprd,sc9836
+      - items:
+          - enum:
+              - sprd,sp9860g-1h10
+          - const: sprd,sc9860
+
+...