dt-bindings: rtc: at91rm9200: convert bindings to json-schema

Convert Real Time Clock for Atmel/Microchip SoCs bindings documentation
to json-schema.

Cc: Rob Herring <robh+dt@kernel.org>
Link: https://lore.kernel.org/r/20191229204421.337612-2-alexandre.belloni@bootlin.comSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/atmel,at91rm9200-rtc.txt

-Atmel AT91RM9200 Real Time Clock
-
-Required properties:
-- compatible: should be: "atmel,at91rm9200-rtc", "atmel,at91sam9x5-rtc" or
-  "microchip,sam9x60-rtc"
-- reg: physical base address of the controller and length of memory mapped
-  region.
-- interrupts: rtc alarm/event interrupt
-- clocks: phandle to input clock.
-
-Example:
-
-rtc@fffffe00 {
-	compatible = "atmel,at91rm9200-rtc";
-	reg = <0xfffffe00 0x100>;
-	interrupts = <1 4 7>;
-	clocks = <&clk32k>;
-};

Documentation/devicetree/bindings/rtc/atmel,at91rm9200-rtc.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/atmel,at91rm9200-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Atmel AT91 RTC Device Tree Bindings
+
+allOf:
+  - $ref: "rtc.yaml#"
+
+maintainers:
+  - Alexandre Belloni <alexandre.belloni@bootlin.com>
+
+properties:
+  compatible:
+    enum:
+      - atmel,at91rm9200-rtc
+      - atmel,at91sam9x5-rtc
+      - microchip,sam9x60-rtc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    rtc@fffffe00 {
+        compatible = "atmel,at91rm9200-rtc";
+        reg = <0xfffffe00 0x100>;
+        interrupts = <1 4 7>;
+        clocks = <&clk32k>;
+    };
+...