dt-bindings: arm: samsung: Convert Exynos System Registers bindings to json-schema

Convert Samsung Exynos System Registers (SYSREG) bindings to DT schema
format using json-schema.
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/arm/samsung/sysreg.txt

-SAMSUNG S5P/Exynos SoC series System Registers (SYSREG)
-
-Properties:
- - compatible : should contain two values. First value must be one from following list:
-		- "samsung,exynos4-sysreg" - for Exynos4 based SoCs,
-		- "samsung,exynos5-sysreg" - for Exynos5 based SoCs.
-		second value must be always "syscon".
- - reg : offset and length of the register set.
-
-Example:
-	syscon@10010000 {
-		compatible = "samsung,exynos4-sysreg", "syscon";
-		reg = <0x10010000 0x400>;
-	};
-
-	syscon@10050000 {
-		compatible = "samsung,exynos5-sysreg", "syscon";
-		reg = <0x10050000 0x5000>;
-	};

Documentation/devicetree/bindings/arm/samsung/sysreg.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/arm/samsung/sysreg.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Samsung S5P/Exynos SoC series System Registers (SYSREG)
+
+maintainers:
+  - Krzysztof Kozlowski <krzk@kernel.org>
+
+# Custom select to avoid matching all nodes with 'syscon'
+select:
+  properties:
+    compatible:
+      contains:
+        enum:
+          - samsung,exynos4-sysreg
+          - samsung,exynos5-sysreg
+  required:
+    - compatible
+
+properties:
+  compatible:
+    allOf:
+      - items:
+          - enum:
+              - samsung,exynos4-sysreg
+              - samsung,exynos5-sysreg
+          - const: syscon
+
+  reg:
+    maxItems: 1
+
+examples:
+  - |
+    syscon@10010000 {
+        compatible = "samsung,exynos4-sysreg", "syscon";
+        reg = <0x10010000 0x400>;
+    };
+
+    syscon@10050000 {
+        compatible = "samsung,exynos5-sysreg", "syscon";
+        reg = <0x10050000 0x5000>;
+    };