[nrf noup] samples: smp_svr: Add nrf54h20dk ext flash sample

Adds a configuration to this sample for external flash on the
nRF54H20DK. It uses 'pure dts' approach, with no Partition Manager.

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

Author: nordic-mik7

samples/subsys/mgmt/mcumgr/smp_svr/boards/nrf54h20dk_nrf54h20_cpuapp_iron_ext_flash.overlay

@@ -0,0 +1,35 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/delete-node/ &slot1_partition;
+
+/ {
+	chosen {
+		extmem-device = &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(512)>;
+		};
+	};
+};
+
+&mram1x {
+	partitions {
+		slot0_partition: partition@3c000 {
+			reg = <0x3c000 DT_SIZE_K(512)>;
+		};
+	};
+};

samples/subsys/mgmt/mcumgr/smp_svr/sample.yaml

@@ -230,3 +230,11 @@ tests:
       - nrf5340dk/nrf5340/cpuapp
     integration_platforms:
       - nrf5340dk/nrf5340/cpuapp
+  sample.mcumgr.smp_svr.serial.nrf54h20dk.ext_flash.pure_dts:
+    extra_args:
+      - EXTRA_CONF_FILE="overlay-serial.conf"
+      - DTC_OVERLAY_FILE="boards/nrf54h20dk_nrf54h20_cpuapp_iron_ext_flash.overlay"
+      - mcuboot_EXTRA_CONF_FILE="boards/nrf54h20dk_nrf54h20_cpuapp_iron_ext_flash.conf"
+      - mcuboot_EXTRA_DTC_OVERLAY_FILE="boards/nrf54h20dk_nrf54h20_cpuapp_iron_ext_flash.overlay"
+    platform_allow:
+      - nrf54h20dk/nrf54h20/cpuapp/iron