Using the nrf52840dk_nrf52840 QSPI NOR flash with MCUboot Zephyr

To enable MCUBoot (and mcumgr) to use the secondary slot stored in the QSPI NOR flash someone can use the provided overlay and configuration files under boot/zephyr/boards.

To build MCUboot:

west build -b nrf52840dk_nrf52840 -d build_boot bootloader/mcuboot/boot/zephyr -- -DDTC_OVERLAY_FILE=$(pwd)/bootloader/mcuboot/boot/zephyr/boards/nrf52840dk_qspi_nor_secondary.overlay -DOVERLAY_CONFIG="$(pwd)/bootloader/mcuboot/boot/zephyr/boards/nrf52840dk_qspi_nor.conf;$(pwd)/bootloader/mcuboot/boot/zephyr/boards/nrf52840dk_qspi_secondary_boot.conf
west flash -d build_boot

To build an app (smp_svr in the example):

west build -b nrf52840dk_nrf52840 zephyr/samples/subsys/mgmt/mcumgr/smp_svr -- -DDTC_OVERLAY_FILE=$(pwd)/bootloader/mcuboot/boot/zephyr/boards/nrf52840dk_qspi_nor_secondary.overlay -DOVERLAY_CONFIG="overlay-bt.conf;$(pwd)/bootloader/mcuboot/boot/zephyr/boards/nrf52840dk_qspi_nor.conf"
west sign -t imgtool -- --key bootloader/mcuboot/root-rsa-2048.pem -v 1.0.0
west flash --hex-file build/zephyr/zephyr.signed.hex