[nrf fromtree] dts: bindings: introduce nordic,nrfs-swext

Introduce nordic NRFS SWEXT power domain bindings and add it to
relevant SoC devicetree files.

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>
(cherry picked from commit cf2e80d)

Author: bjarki-andreasen

dts/bindings/power-domain/nordic,nrfs-swext.yaml

@@ -0,0 +1,26 @@
+# Copyright 2025 Nordic Semiconductor
+# SPDX-License-Identifier: Apache-2.0
+
+description: Nordic NRFS SWEXT power domain
+
+compatible: "nordic,nrfs-swext"
+
+include: power-domain.yaml
+
+properties:
+  "#power-domain-cells":
+    const: 0
+
+  max-current-ua:
+    type: int
+    description: Maxmimum supported current in microamps.
+    required: true
+
+  current-limit-ua:
+    type: int
+    description: Maxmimum allowed current in microamps.
+    required: true
+
+  power-down-clamp:
+    type: boolean
+    description: Enable ground clamp on output when powered down.

dts/vendor/nordic/nrf54h20.dtsi

@@ -252,6 +252,15 @@
 		};
 	};
 
+	swext: swext {
+		compatible = "nordic,nrfs-swext";
+		status = "disabled";
+		max-current-ua = <7500>;
+		current-limit-ua = <7500>;
+		zephyr,pm-device-runtime-auto;
+		#power-domain-cells = <0>;
+	};
+
 	soc {
 		#address-cells = <1>;
 		#size-cells = <1>;