dt-bindings: gpio: Convert ti,keystone-dsp-gpio to DT schema

Convert the TI Keystone DSP GPIO binding to DT schema format. The
"ti,syscon-dev" property was wrong and should be "gpio,syscon-dev"
instead.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://lore.kernel.org/r/20250714202850.3011952-1-robh@kernel.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Author: robherring

Documentation/devicetree/bindings/gpio/gpio-dsp-keystone.txt

@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/gpio/ti,keystone-dsp-gpio.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Keystone 2 DSP GPIO controller
+
+maintainers:
+  - Grygorii Strashko <grygorii.strashko@ti.com>
+
+description: |
+  HOST OS userland running on ARM can send interrupts to DSP cores using
+  the DSP GPIO controller IP. It provides 28 IRQ signals per each DSP core.
+  This is one of the component used by the IPC mechanism used on Keystone SOCs.
+
+  For example TCI6638K2K SoC has 8 DSP GPIO controllers:
+   - 8 for C66x CorePacx CPUs 0-7
+
+  Keystone 2 DSP GPIO controller has specific features:
+  - each GPIO can be configured only as output pin;
+  - setting GPIO value to 1 causes IRQ generation on target DSP core;
+  - reading pin value returns 0 - if IRQ was handled or 1 - IRQ is still
+    pending.
+
+properties:
+  compatible:
+    const: ti,keystone-dsp-gpio
+
+  reg:
+    maxItems: 1
+
+  gpio-controller: true
+
+  '#gpio-cells':
+    const: 2
+
+  gpio,syscon-dev:
+    description:
+      Phandle and offset of device's specific registers within the syscon state
+      control registers
+    $ref: /schemas/types.yaml#/definitions/phandle-array
+    items:
+      - items:
+          - description: phandle to syscon
+          - description: register offset within state control registers
+
+required:
+  - compatible
+  - reg
+  - gpio-controller
+  - '#gpio-cells'
+  - gpio,syscon-dev
+
+additionalProperties: false
+
+examples:
+  - |
+    gpio@240 {
+        compatible = "ti,keystone-dsp-gpio";
+        reg = <0x240 0x4>;
+        gpio-controller;
+        #gpio-cells = <2>;
+        gpio,syscon-dev = <&devctrl 0x240>;
+    };