+boot_mode selects which boot script will be used by 'bootcmd' to
+ boot the application (Linux)
+ supported values:
+ nand: (default) load kernel from NAND partition 'linux'
+ and mount rootfs (fstype UBIFS)
+ from partition 'rootfs'.
+ mmc: load kernel from file 'uImage' on first
+ partition (FAT) on (first) SD/MMC card
+ and mount rootfs (fstype autodetected)
+ from second partition.
+ net: load kernel image via tftp (file uImage)
+ and mount rootfs via NFS. This requires
+ the additional variables 'nfsroot'
+ (path to rootfs on NFS server) and
+ 'nfs_server' (hostname or IP address of
+ NFS server) to be set.
+ jffs2: (legacy) load kernel from NAND partition 'linux'
+ and mount rootfs (fstype JFFS2)
+ from partition 'rootfs'.
+
+cpu_clk <CPU freq [MHz]> CPU clock frequency set after boot.
+
+touchpanel {tsc2007|edt-ft5x06|egalax_ts} type of touchpanel.
+ No touchpanel will be enabled when unset.
+
+otg_mode [host|device|none] operation mode of the USBOTG port
+
+video_mode <one of the display names from the Glyn Family Concept or
+ a video mode as understood by Linux fb_find_mode() function
+ (e.g.: 640x480MR-24@60)>
+ LCD interface will be disabled when unset.