tests/drivers/retained_mem/api/boards/qemu_cortex_m3.overlay

#include <common/mem.h>

/ {
	sram@2000FFE0 {
		compatible = "zephyr,memory-region", "mmio-sram";
		reg = <0x2000FFE0 0x20>;
		zephyr,memory-region = "Retention";
		status = "okay";

		retainedmem0: retainedmem {
			compatible = "zephyr,retained-ram";
			status = "okay";
		};
	};

	aliases {
		retainedmemtestdevice = &retainedmem0;
	};
};

&sram0 {
	reg = <0x20000000 DT_SIZE_K(60)>;
};