u-boot/tools/binman/test/29_x86-rom.dts

/dts-v1/;

/ {
	#address-cells = <1>;
	#size-cells = <1>;

	binman {
		sort-by-pos;
		end-at-4gb;
		size = <16>;
		u-boot {
			pos = <0xfffffff0>;
		};

		u-boot-spl {
			pos = <0xfffffff7>;
		};
	};
};