dt-bindings: soc: sophgo: add RTC support for Sophgo CV1800 series

Add RTC devicetree binding for Sophgo CV1800 series SoC. The device is
called RTC, but contains control registers of other HW blocks in its
address space, most notably of Power-on-Reset (PoR) module, DW8051 IP
(MCU core), accompanying SRAM, hence putting it in SoC subsystem.

Signed-off-by: Jingbao Qiu <qiujingbao.dlmu@gmail.com>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Inochi Amaoto <inochiama@gmail.com>
Link: https://lore.kernel.org/r/20250315224921.3627852-2-alexander.sverdlin@gmail.com
Signed-off-by: Inochi Amaoto <inochiama@gmail.com>
Signed-off-by: Chen Wang <unicorn_wang@outlook.com>
Signed-off-by: Chen Wang <wangchen20@iscas.ac.cn>

Documentation/devicetree/bindings/soc/sophgo/sophgo,cv1800b-rtc.yaml

@@ -0,0 +1,86 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/sophgo/sophgo,cv1800b-rtc.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Real Time Clock of the Sophgo CV1800 SoC
+
+description:
+  The RTC (Real Time Clock) is an independently powered module in the chip. It
+  contains a 32KHz oscillator and a Power-On-Reset (POR) sub-module, which can
+  be used for time display and scheduled alarm produce. In addition, the
+  hardware state machine provides triggering and timing control for chip
+  power-on, power-off and reset.
+
+  Furthermore, the 8051 subsystem is located within RTCSYS and is independently
+  powered. System software can use the 8051 to manage wake conditions and wake
+  the system while the system is asleep, and communicate with external devices
+  through peripheral controllers.
+
+  Technical Reference Manual available at
+    https://github.com/sophgo/sophgo-doc/tree/main/SG200X/TRM
+
+maintainers:
+  - sophgo@lists.linux.dev
+
+allOf:
+  - $ref: /schemas/rtc/rtc.yaml#
+
+properties:
+  compatible:
+    items:
+      - const: sophgo,cv1800b-rtc
+      - const: syscon
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: RTC Alarm
+      - description: RTC Longpress
+      - description: VBAT DET
+
+  interrupt-names:
+    items:
+      - const: alarm
+      - const: longpress
+      - const: vbat
+
+  clocks:
+    items:
+      - description: RTC clock source
+      - description: DW8051 MCU clock source
+
+  clock-names:
+    items:
+      - const: rtc
+      - const: mcu
+
+required:
+  - compatible
+  - reg
+  - interrupts
+  - interrupt-names
+  - clocks
+  - clock-names
+
+unevaluatedProperties: false
+
+examples:
+  - |
+    #include <dt-bindings/clock/sophgo,cv1800.h>
+    #include <dt-bindings/interrupt-controller/irq.h>
+
+    rtc@5025000 {
+        compatible = "sophgo,cv1800b-rtc", "syscon";
+        reg = <0x5025000 0x2000>;
+        interrupts = <17 IRQ_TYPE_LEVEL_HIGH>,
+                     <18 IRQ_TYPE_LEVEL_HIGH>,
+                     <19 IRQ_TYPE_LEVEL_HIGH>;
+        interrupt-names = "alarm", "longpress", "vbat";
+        clocks = <&clk CLK_RTC_25M>,
+                 <&clk CLK_SRC_RTC_SYS_0>;
+        clock-names = "rtc", "mcu";
+    };