[PATCH v3 1/2] dt-bindings: timer: Add Realtek SYSTIMER

[Hao-Wen Ting <haowen.ting@realtek.com>]

Add device tree binding documentation for the Realtek SYSTIMER, a 64-bit
timer that can be used as a tick broadcast timer on multi-core Realtek
SoCs.

The SYSTIMER remains active during deep CPU idle states where local
timers are powered off, allowing all CPUs to enter power-cut idle states
simultaneously for improved power efficiency. The timer operates at a
fixed 1MHz frequency and supports oneshot mode for tick broadcast
functionality.

Signed-off-by: Hao-Wen Ting <haowen.ting@realtek.com>
---
 .../timer/realtek,rtd1625-systimer.yaml       | 55 +++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml

diff --git a/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml b/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml
new file mode 100644
index 000000000000..b7702ba52437
--- /dev/null
+++ b/Documentation/devicetree/bindings/timer/realtek,rtd1625-systimer.yaml
@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/timer/realtek,rtd1625-systimer.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek System Timer
+
+maintainers:
+  - Hao-Wen Ting <haowen.ting@realtek.com>
+
+description: |
+  The Realtek SYSTIMER (System Timer) is a 64-bit timer that can be used as
+  a tick broadcast timer on multi-core Realtek SoCs. It remains active during
+  deep CPU idle states where local timers are powered off, allowing all CPUs
+  to enter power-cut idle states simultaneously for better power efficiency.
+
+  The timer operates at a fixed 1MHz frequency and supports oneshot mode
+  for tick broadcast functionality.
+
+  The SYSTIMER hardware for both RTD1625 and RTD1635 SoCs has identical register
+  layout and IRQ configuration. The driver therefore matches both compatibles
+  without special handling.
+
+properties:
+  compatible:
+    items:
+      - enum:
+          - realtek,rtd1625-systimer
+          - realtek,rtd1635-systimer
+      - const: realtek,rtd1625-systimer
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    maxItems: 1
+
+required:
+  - compatible
+  - reg
+  - interrupts
+
+additionalProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
+
+    timer@89420 {
+        compatible = "realtek,rtd1635-systimer",
+                     "realtek,rtd1625-systimer";
+        reg = <0x89420 0x18>;
+        interrupts = <GIC_SPI 112 IRQ_TYPE_LEVEL_HIGH>;
+    };
-- 
2.34.1