dt-bindings: rtc: m41t80: Convert text schema to YAML one

Convert the m41t80 text schema to YAML schema.

Add "#clock-cells" requirement, which is required by clock-output-names.
Signed-off-by: Marek Vasut <marex@denx.de>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221211205124.23823-1-marex@denx.deSigned-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/rtc-m41t80.txt

-ST M41T80 family of RTC and compatible
-
-Required properties:
-- compatible: should be one of:
-	"st,m41t62",
-	"st,m41t65",
-	"st,m41t80",
-	"st,m41t81",
-	"st,m41t81s",
-	"st,m41t82",
-	"st,m41t83",
-	"st,m41t84",
-	"st,m41t85",
-	"st,m41t87",
-	"microcrystal,rv4162",
-- reg: I2C bus address of the device
-
-Optional properties:
-- interrupts: rtc alarm interrupt.
-- clock-output-names: From common clock binding to override the default output
-                      clock name
-- wakeup-source: Enables wake up of host system on alarm
-
-Optional child node:
-- clock: Provide this if the square wave pin is used as boot-enabled fixed clock.
-
-Example:
-	rtc@68 {
-		compatible = "st,m41t80";
-		reg = <0x68>;
-		interrupt-parent = <&UIC0>;
-		interrupts = <0x9 0x8>;
-
-		clock {
-			compatible = "fixed-clock";
-			#clock-cells = <0>;
-			clock-frequency = <32768>;
-		};
-	};

Documentation/devicetree/bindings/rtc/st,m41t80.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/st,m41t80.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: ST M41T80 family of RTC and compatible
+
+maintainers:
+  - Alexandre Belloni <alexandre.belloni@bootlin.com>
+
+properties:
+  compatible:
+    enum:
+      - st,m41t62
+      - st,m41t65
+      - st,m41t80
+      - st,m41t81
+      - st,m41t81s
+      - st,m41t82
+      - st,m41t83
+      - st,m41t84
+      - st,m41t85
+      - st,m41t87
+      - microcrystal,rv4162
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  "#clock-cells":
+    const: 1
+
+  clock-output-names:
+    maxItems: 1
+    description: From common clock binding to override the default output clock name.
+
+  clock:
+    type: object
+    $ref: /schemas/clock/fixed-clock.yaml#
+    properties:
+      clock-frequency:
+        const: 32768
+
+allOf:
+  - $ref: rtc.yaml
+
+unevaluatedProperties: false
+
+required:
+  - compatible
+  - reg
+
+examples:
+  - |
+    i2c {
+      #address-cells = <1>;
+      #size-cells = <0>;
+      rtc@68 {
+        compatible = "st,m41t80";
+        reg = <0x68>;
+        interrupt-parent = <&UIC0>;
+        interrupts = <0x9 0x8>;
+
+        clock {
+          compatible = "fixed-clock";
+          #clock-cells = <0>;
+          clock-frequency = <32768>;
+        };
+      };
+    };