dts: nordic,gpio-pins: Implementation of gpio-pins binding

This commit adds nordic,gpio-pins binding.
This binding may be used to properly generate pins access for
the domain using UICR.
Additionally the pins defined this way may be accessed
via devicetree macros.

No driver is implemented with this binding.

Signed-off-by: Radoslaw Koppel <radoslaw.koppel@nordicsemi.no>
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>

Author: rakons

dts/bindings/gpio/nordic,gpio-pins.yaml

@@ -0,0 +1,18 @@
+# Copyright (c) 2023 Nordic Semiconductor ASA
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+
+description: |
+  This allows to define the pin of the GPIO to be owned by the domain.
+  It does not provide any specyfic driver.
+  Its function is to allow us to use two functionalities:
+
+  1. Generate the right UICR marking the domain to own the selected pin.
+  2. Access to pins by the macros from zephyr/devicetree/gpio.h file
+     increasing the hardware abstraction this way.
+
+compatible: "nordic,gpio-pins"
+
+properties:
+  gpios:
+    type: phandle-array
+    required: true