dt-bindings: gpio: realtek: Add realtek,rtd1625-gpio

Add the device tree bindings for the Realtek DHC (Digital Home Center)
RTD1625 GPIO controllers.

The RTD1625 GPIO controller features a per-pin register architecture
that differs significantly from previous generations. It utilizes
separate register blocks for GPIO configuration and interrupt control.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Tzuyi Chang <tychang@realtek.com>
Signed-off-by: Yu-Chun Lin <eleanor.lin@realtek.com>
Link: https://patch.msgid.link/20260622092335.1166876-2-eleanor.lin@realtek.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

Documentation/devicetree/bindings/gpio/realtek,rtd1625-gpio.yaml

@@ -0,0 +1,71 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+# Copyright 2023 Realtek Semiconductor Corporation
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/realtek,rtd1625-gpio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Realtek DHC RTD1625 GPIO controller
+
+maintainers:
+  - Tzuyi Chang <tychang@realtek.com>
+
+description: |
+  GPIO controller for the Realtek RTD1625 SoC, featuring a per-pin register
+  architecture that differs significantly from earlier RTD series controllers.
+  Each GPIO has dedicated registers for configuration (direction, input/output
+  values, debounce), and interrupt control supporting edge and level detection
+  modes.
+
+properties:
+  compatible:
+    enum:
+      - realtek,rtd1625-iso-gpio
+      - realtek,rtd1625-isom-gpio
+
+  reg:
+    maxItems: 1
+
+  interrupts:
+    items:
+      - description: Interrupt number of the assert GPIO interrupt, which is
+                     triggered when there is a rising edge.
+      - description: Interrupt number of the deassert GPIO interrupt, which is
+                     triggered when there is a falling edge.
+      - description: Interrupt number of the level-sensitive GPIO interrupt,
+                     triggered by a configured logic level.
+
+  interrupt-controller: true
+
+  "#interrupt-cells":
+    const: 2
+
+  gpio-ranges: true
+
+  gpio-controller: true
+
+  "#gpio-cells":
+    const: 2
+
+required:
+  - compatible
+  - reg
+  - gpio-ranges
+  - gpio-controller
+  - "#gpio-cells"
+
+additionalProperties: false
+
+examples:
+  - |
+    gpio@89100 {
+      compatible = "realtek,rtd1625-isom-gpio";
+      reg = <0x89100 0x30>;
+      interrupt-parent = <&iso_m_irq_mux>;
+      interrupts = <0>, <1>, <2>;
+      interrupt-controller;
+      #interrupt-cells = <2>;
+      gpio-ranges = <&isom_pinctrl 0 0 4>;
+      gpio-controller;
+      #gpio-cells = <2>;
+    };