dt-bindings: rtc: Convert Allwinner A31 RTC to a schema

The newer 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,sun6i-a31-rtc.yaml

+# SPDX-License-Identifier: GPL-2.0
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/allwinner,sun6i-a31-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Allwinner A31 RTC Device Tree Bindings
+
+maintainers:
+  - Chen-Yu Tsai <wens@csie.org>
+  - Maxime Ripard <maxime.ripard@bootlin.com>
+
+properties:
+  "#clock-cells":
+    const: 1
+
+  compatible:
+    oneOf:
+      - const: allwinner,sun6i-a31-rtc
+      - const: allwinner,sun8i-a23-rtc
+      - const: allwinner,sun8i-h3-rtc
+      - items:
+          - const: allwinner,sun8i-r40-rtc
+          - const: allwinner,sun8i-h3-rtc
+      - const: allwinner,sun8i-v3-rtc
+      - const: allwinner,sun50i-h5-rtc
+      - items:
+          - const: allwinner,sun50i-a64-rtc
+          - const: allwinner,sun8i-h3-rtc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: RTC Alarm 0
+      - description: RTC Alarm 1
+
+  clocks:
+    maxItems: 1
+
+  clock-output-names:
+    minItems: 1
+    maxItems: 3
+    description:
+      The RTC provides up to three clocks
+        - the Low Frequency Oscillator or LOSC, at index 0,
+        - the Low Frequency Oscillator External output (X32KFOUT in
+          the datasheet), at index 1,
+        - the Internal Oscillator, at index 2.
+
+allOf:
+  - $ref: "rtc.yaml#"
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: allwinner,sun6i-a31-rtc
+
+    then:
+      properties:
+        clock-output-names:
+          minItems: 1
+          maxItems: 1
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - allwinner,sun8i-a23-rtc
+              - allwinner,sun8i-v3-rtc
+
+    then:
+      properties:
+        clock-output-names:
+          minItems: 2
+          maxItems: 2
+
+  - if:
+      properties:
+        compatible:
+          contains:
+            enum:
+              - allwinner,sun8i-h3-rtc
+              - allwinner,sun50i-h5-rtc
+
+    then:
+      properties:
+        clock-output-names:
+          minItems: 3
+          maxItems: 3
+
+required:
+  - "#clock-cells"
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - clock-output-names
+
+additionalProperties: false
+
+examples:
+  - |
+    rtc: rtc@1f00000 {
+        compatible = "allwinner,sun6i-a31-rtc";
+        reg = <0x01f00000 0x400>;
+        interrupts = <0 40 4>, <0 41 4>;
+        clock-output-names = "osc32k";
+        clocks = <&ext_osc32k>;
+        #clock-cells = <1>;
+    };
+
+...

Documentation/devicetree/bindings/rtc/sun6i-rtc.txt

-* sun6i Real Time Clock
-
-RTC controller for the Allwinner A31
-
-Required properties:
-- compatible	: Should be one of the following combinations:
-		    - "allwinner,sun6i-a31-rtc"
-		    - "allwinner,sun8i-a23-rtc"
-		    - "allwinner,sun8i-h3-rtc"
-		    - "allwinner,sun8i-r40-rtc", "allwinner,sun8i-h3-rtc"
-		    - "allwinner,sun8i-v3-rtc"
-		    - "allwinner,sun50i-a64-rtc", "allwinner,sun8i-h3-rtc"
-		    - "allwinner,sun50i-h5-rtc"
-
-		  Where there are two or more compatible strings, this
-		  denotes the hardware covered by the most specific one
-		  is backward-compatible with the latter ones, and the
-		  implementation for the latter ones can be used, albeit
-		  with reduced functionality.
-
-- reg		: physical base address of the controller and length of
-		  memory mapped region.
-- interrupts	: IRQ lines for the RTC alarm 0 and alarm 1, in that order.
-
-Required properties for new device trees
-- clocks	: phandle to the 32kHz external oscillator
-- clock-output-names : names of up to three clock outputs. See below.
-- #clock-cells  : must be equal to 1.
-
-The RTC provides the following clocks at the given indices:
-- 0: LOSC
-- 1: LOSC external output, known as X32KFOUT in the datasheet.
-     This clock is not available on the A31 and is deprecated for old
-     device trees still using the "allwinner,sun6i-a31-rtc" compatible.
-- 2: InternalOSC, or internal RC oscillator (A64/H3/H5 only)
-
-Example:
-
-rtc: rtc@1f00000 {
-	compatible = "allwinner,sun6i-a31-rtc";
-	reg = <0x01f00000 0x400>;
-	interrupts = <0 40 4>, <0 41 4>;
-	clock-output-names = "osc32k";
-	clocks = <&ext_osc32k>;
-	#clock-cells = <1>;
-};