openwrt/target/linux/mxs/image/Config.in

config MXS_SD_BOOT_PARTSIZE
	int "Boot (SD Card) filesystem partition size (in MB)"
	depends on TARGET_mxs
	default 8
	help
	    On the Olimex OLinuXino boards, mainline U-Boot loads the
	    linux kernel and device tree file from a FAT partition.
	    The default value of 8 MB should be more than adequate.