dt-bindings: rtc: convert at91sam9 bindings to json-schema

Convert RTC binding for Atmel/Microchip SoCs to Device Tree Schema
format.
Signed-off-by: Sergiu Moga <sergiu.moga@microchip.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20220304161159.147784-4-sergiu.moga@microchip.com

Documentation/devicetree/bindings/rtc/atmel,at91sam9-rtc.txt

-Atmel AT91SAM9260 Real Time Timer
-
-Required properties:
-- compatible: should be one of the following:
-	- "atmel,at91sam9260-rtt"
-	- "microchip,sam9x60-rtt", "atmel,at91sam9260-rtt"
-- reg: should encode the memory region of the RTT controller
-- interrupts: rtt alarm/event interrupt
-- clocks: should contain the 32 KHz slow clk that will drive the RTT block.
-- atmel,rtt-rtc-time-reg: should encode the GPBR register used to store
-	the time base when the RTT is used as an RTC.
-	The first cell should point to the GPBR node and the second one
-	encode the offset within the GPBR block (or in other words, the
-	GPBR register used to store the time base).
-
-
-Example:
-
-rtt@fffffd20 {
-	compatible = "atmel,at91sam9260-rtt";
-	reg = <0xfffffd20 0x10>;
-	interrupts = <1 4 7>;
-	clocks = <&clk32k>;
-	atmel,rtt-rtc-time-reg = <&gpbr 0x0>;
-};

Documentation/devicetree/bindings/rtc/atmel,at91sam9-rtc.yaml

+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+# Copyright (C) 2022 Microchip Technology, Inc. and its subsidiaries
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/atmel,at91sam9-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Atmel AT91 RTT Device Tree Bindings
+
+allOf:
+  - $ref: "rtc.yaml#"
+
+maintainers:
+  - Alexandre Belloni <alexandre.belloni@bootlin.com>
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - const: atmel,at91sam9260-rtt
+      - items:
+          - const: microchip,sam9x60-rtt
+          - const: atmel,at91sam9260-rtt
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  clocks:
+    maxItems: 1
+
+  atmel,rtt-rtc-time-reg:
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    items:
+      - items:
+          - description: Phandle to the GPBR node.
+          - description: Offset within the GPBR block.
+    description:
+      Should encode the GPBR register used to store the time base when the
+      RTT is used as an RTC. The first cell should point to the GPBR node
+      and the second one encodes the offset within the GPBR block (or in
+      other words, the GPBR register used to store the time base).
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - clocks
+  - atmel,rtt-rtc-time-reg
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    rtc@fffffd20 {
+        compatible = "atmel,at91sam9260-rtt";
+        reg = <0xfffffd20 0x10>;
+        interrupts = <1 IRQ_TYPE_LEVEL_HIGH 7>;
+        clocks = <&clk32k>;
+        atmel,rtt-rtc-time-reg = <&gpbr 0x0>;
+    };