dt-bindings: rtc: Add support for ATCRTC100 RTC

Document Device Tree bindings for the Andes ATCRTC100 Real-Time Clock.

Signed-off-by: CL Wang <cl634@andestech.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20250915031439.2680364-2-cl634@andestech.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Documentation/devicetree/bindings/rtc/andestech,atcrtc100.yaml

@@ -0,0 +1,43 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/rtc/andestech,atcrtc100.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Andes ATCRTC100 Real-Time Clock
+
+maintainers:
+  - CL Wang <cl634@andestech.com>
+
+allOf:
+  - $ref: rtc.yaml#
+
+properties:
+  compatible:
+    enum:
+      - andestech,atcrtc100
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: Periodic timekeeping interrupt
+      - description: RTC alarm interrupt
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    rtc@f0300000 {
+        compatible = "andestech,atcrtc100";
+        reg = <0xf0300000 0x100>;
+        interrupts = <1 IRQ_TYPE_LEVEL_HIGH>, <2 IRQ_TYPE_LEVEL_HIGH>;
+    };