dt-bindings: rtc: Convert apm,xgene-rtc to DT schema

Convert the APM XGene RTC binding to DT schema format. It's a
straight-forward conversion.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250924222848.2949235-1-robh@kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Author: robherring

Documentation/devicetree/bindings/rtc/apm,xgene-rtc.yaml

@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/apm,xgene-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: APM X-Gene Real Time Clock
+
+maintainers:
+  - Khuong Dinh <khuong@os.amperecomputing.com>
+
+properties:
+  compatible:
+    const: apm,xgene-rtc
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+  '#clock-cells':
+    const: 1
+
+  clocks:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - '#clock-cells'
+  - clocks
+
+additionalProperties: false
+
+examples:
+  - |
+    rtc@10510000 {
+        compatible = "apm,xgene-rtc";
+        reg = <0x10510000 0x400>;
+        interrupts = <0x0 0x46 0x4>;
+        #clock-cells = <1>;
+        clocks = <&rtcclk 0>;
+    };