[nrf noup] boot/zephyr: add nrf54h20dk ext flash configs

This commit adds overlay and configuration files for the
nRF54H20 DK with external flash support.

Signed-off-by: Michal Kozikowski <[email protected]>

Author: nordic-mik7

boot/zephyr/boards/nrf54h20dk_nrf54h20_cpuapp_iron_ext_flash.conf

@@ -0,0 +1,10 @@
+# Copyright (c) 2025 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+CONFIG_SPI=y
+CONFIG_FLASH=y
+CONFIG_BOOT_MAX_IMG_SECTORS_AUTO=n
+CONFIG_BOOT_MAX_IMG_SECTORS=512
+CONFIG_FLASH_MSPI_NOR_LAYOUT_PAGE_SIZE=4096

boot/zephyr/boards/nrf54h20dk_nrf54h20_cpuapp_iron_ext_flash.overlay

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/delete-node/ &slot1_partition;
+
+/ {
+	chosen {
+		nordic,pm-ext-flash = &mx25uw63;
+	};
+};
+
+&mx25uw63 {
+	status = "okay";
+	partitions {
+		compatible = "fixed-partitions";
+		#address-cells = <1>;
+		#size-cells = <1>;
+
+		slot1_partition: partition@0 {
+			label = "image-1";
+			reg = <0x0 DT_SIZE_K(336)>;
+		};
+	};
+};