dt-bindings: rtc: Convert Allwinner A10 RTC to a schema

The older Allwinner SoCs have an embedded RTC supported in Linux, with a
matching Device Tree binding.

Now that we have the DT validation in place, let's convert the device tree
bindings for that controller over to a YAML schemas.
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/allwinner,sun4i-a10-rtc.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/allwinner,sun4i-a10-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Allwinner A10 RTC Device Tree Bindings
+
+allOf:
+  - $ref: "rtc.yaml#"
+
+maintainers:
+  - Chen-Yu Tsai <wens@csie.org>
+  - Maxime Ripard <maxime.ripard@bootlin.com>
+
+properties:
+  compatible:
+    enum:
+      - allwinner,sun4i-a10-rtc
+      - allwinner,sun7i-a20-rtc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    rtc: rtc@1c20d00 {
+        compatible = "allwinner,sun4i-a10-rtc";
+        reg = <0x01c20d00 0x20>;
+        interrupts = <24>;
+    };
+
+...

Documentation/devicetree/bindings/rtc/sunxi-rtc.txt

-* sun4i/sun7i Real Time Clock
-
-RTC controller for the Allwinner A10/A20
-
-Required properties:
-- compatible : Should be "allwinner,sun4i-a10-rtc" or "allwinner,sun7i-a20-rtc"
-- reg: physical base address of the controller and length of memory mapped
-  region.
-- interrupts: IRQ line for the RTC.
-
-Example:
-
-rtc: rtc@1c20d00 {
-	compatible = "allwinner,sun4i-a10-rtc";
-	reg = <0x01c20d00 0x20>;
-	interrupts = <24>;
-};