samples: bluetooth: central_uart: sign nRF54LM20 Dongle image

nRF54LM20 Dongle image needs to be signed to be programmable with
nRF Util (that uses MCUBoot firmware loader mode). As for now,
this implies that MCUBoot build must be enabled for the dongle.

Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>
Signed-off-by: Damian Krolik <damian.krolik@nordicsemi.no>

Author: nvlsianpu

samples/bluetooth/central_uart/Kconfig.sysbuild

@@ -13,4 +13,29 @@ config NRF_DEFAULT_IPC_RADIO
 config NETCORE_IPC_RADIO_BT_HCI_IPC
 	default y
 
+config SAMPLE_NRF54LM20DONGLE_BOOTLOADER
+	bool
+	default y
+	depends on BOARD_NRF54LM20DONGLE
+	select MCUBOOT_MODE_FIRMWARE_UPDATER_BOOT_MODE_ENTRANCE
+	select MCUBOOT_SIGNATURE_USING_KMU
+	select MCUBOOT_GENERATE_DEFAULT_KEY_FILE
+	select BOOT_SIGNATURE_TYPE_PURE
+
+if SAMPLE_NRF54LM20DONGLE_BOOTLOADER
+
+choice BOOTLOADER
+	default BOOTLOADER_MCUBOOT
+endchoice
+
+choice MCUBOOT_MODE
+	default MCUBOOT_MODE_FIRMWARE_UPDATER
+endchoice
+
+choice FIRMWARE_LOADER
+	default FIRMWARE_LOADER_IMAGE_USB_MCUMGR
+endchoice
+
+endif # SAMPLE_NRF54LM20DONGLE_BOOTLOADER
+
 source "share/sysbuild/Kconfig"

samples/bluetooth/central_uart/nrf54lm20dongle_dfu_partitions.dtsi

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2026 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/* This file modifies RRAM partitioning for MCUboot and firmware loader by
+ * extending slot0_partition (application image) to the end of RRAM.
+ *
+ * While the application may use extra partitions, such as storage_partition
+ * defined by default, this partitioning of application-dedicated region is
+ * irrelevant to the bootloader images.
+ */
+
+/delete-node/ &storage_partition;
+
+&slot0_partition {
+	/* Start matches board layout */
+	reg = <0x23000 DT_SIZE_K(1896)>;
+
+};

samples/bluetooth/central_uart/sysbuild/mcuboot/boards/nrf54lm20dongle_nrf54lm20b_cpuapp.conf

@@ -0,0 +1,15 @@
+#
+# Copyright (c) 2026 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+CONFIG_SYS_CLOCK_EXISTS=n
+CONFIG_NRF_GRTC_TIMER=n
+CONFIG_CRACEN_IKG=n
+CONFIG_FPROTECT=y
+
+# Disable run-time CRACEN provisioning of TRNG data.
+# KMU slots 248, 249 shall be pre-provisioned while programming with secret TRNG values instead.
+CONFIG_CRACEN_PROVISION_PROT_RAM_INV_SLOTS_ON_INIT=n
+
+CONFIG_NRF_RRAM_WRITE_BUFFER_SIZE=32

samples/bluetooth/central_uart/sysbuild/mcuboot/boards/nrf54lm20dongle_nrf54lm20b_cpuapp.overlay

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2026 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/ {
+	chosen {
+		zephyr,code-partition = &boot_partition;
+	};
+};
+
+/* ensure same RRAM layout in firmware_loader as in MCUboot */
+#include "../../../nrf54lm20dongle_dfu_partitions.dtsi"

samples/bluetooth/central_uart/sysbuild/mcuboot/prj.conf

@@ -0,0 +1,47 @@
+#
+# Copyright (c) 2026 Nordic Semiconductor ASA
+#
+# SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+#
+
+CONFIG_BOOT_FIRMWARE_LOADER_ENTRANCE_GPIO=y
+CONFIG_BOOT_FIRMWARE_LOADER_NO_APPLICATION=y
+
+CONFIG_PM=n
+
+CONFIG_MAIN_STACK_SIZE=10240
+
+CONFIG_BOOT_SWAP_SAVE_ENCTLV=n
+CONFIG_BOOT_ENCRYPT_IMAGE=n
+
+CONFIG_BOOT_UPGRADE_ONLY=n
+CONFIG_BOOT_BOOTSTRAP=n
+
+CONFIG_FLASH=y
+CONFIG_GPIO=y
+
+### Decrease footprint by ~4 KB in comparison to CBPRINTF_COMPLETE=y
+CONFIG_CBPRINTF_NANO=y
+### Use picolibc to reduce flash usage
+CONFIG_PICOLIBC=y
+### Disable malloc arena because we don't need it
+CONFIG_COMMON_LIBC_MALLOC_ARENA_SIZE=0
+
+# Reduce memory consumption
+CONFIG_BOOT_BANNER=n
+CONFIG_NCS_BOOT_BANNER=n
+CONFIG_CLOCK_CONTROL=n
+CONFIG_NRF_GRTC_START_SYSCOUNTER=n
+CONFIG_SPI_NOR=n
+CONFIG_SERIAL=n
+CONFIG_CONSOLE=n
+CONFIG_UART_CONSOLE=n
+CONFIG_PRINTK=n
+CONFIG_USE_SEGGER_RTT=n
+
+# Activate Link Time Optimization (LTO)
+CONFIG_LTO=y
+CONFIG_ISR_TABLES_LOCAL_DECLARATION=y
+
+# Improve debugging experience by disabling reset on fatal error
+CONFIG_RESET_ON_FATAL_ERROR=n

samples/bluetooth/central_uart/sysbuild/usb_mcumgr_nrf54lm20dongle_nrf54lm20b_cpuapp.conf

@@ -0,0 +1,5 @@
+CONFIG_CDC_ACM_SERIAL_VID=0x1915
+CONFIG_CDC_ACM_SERIAL_PID=0x541A
+CONFIG_CDC_ACM_SERIAL_MANUFACTURER_STRING="Nordic Semiconductor ASA"
+CONFIG_CDC_ACM_SERIAL_PRODUCT_STRING="nRF54LM20 Dongle Bootloader"
+CONFIG_MCUMGR_GRP_ZBASIC_STORAGE_ERASE=n

samples/bluetooth/central_uart/sysbuild/usb_mcumgr_nrf54lm20dongle_nrf54lm20b_cpuapp.overlay

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2026 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/ {
+	chosen {
+		/delete-property/ zephyr,console;
+		/delete-property/ zephyr,shell-uart;
+		/delete-property/ zephyr,bt-mon-uart;
+		/delete-property/ zephyr,bt-c2h-uart;
+	};
+};
+
+&zephyr_udc0 {
+	/delete-node/ board_cdc_acm_uart;
+};
+
+/* ensure same RRAM layout in firmware_loader as in MCUboot */
+#include "../nrf54lm20dongle_dfu_partitions.dtsi"