Board: Nokia RX-51 aka N900
  
  This board definition results in a u-boot.bin which can be chainloaded
  from NOLO in qemu or on a real N900. It does very little hardware config
  because NOLO has already configured the board. Only needed is enabling
  internal eMMC memory via twl4030 regulator which is not enabled by NOLO.
  
  NOLO is expecting a kernel image and will treat any image it finds in
  onenand as such. This u-boot is intended to be flashed to the N900 like
  a kernel. In order to transparently boot the original kernel, it will be
  appended to u-boot.bin at 0x40000. NOLO will load the entire image into
  (random) memory and execute u-boot, which saves hw revision, boot reason
  and boot mode ATAGs set by NOLO. Then the bootscripts will attempt to load
  uImage or boot.scr from a fat, ext2/ext3 or ext4 filesystem in external
  SD card or internal eMMC memory. If this fails or keyboard is closed then
  the appended kernel image will be booted using some generated and some
  stored ATAGs (see boot order).
  
  There is support for hardware watchdog. Hardware watchdog is started by
  NOLO so u-boot must kick watchdog to prevent reboot device (but not very
  often, max every 2 seconds). There is also support for framebuffer display
  output with ANSI espace codes and the N900 HW keyboard input. USB tty works
  but is disabled because it prevents the current Maemo kernel from booting.
  
  When U-Boot is starting it enable IBE bit in Auxiliary Control Register,
  which is needed for Thumb-2 ISA support. It is workaround for errata 430973.
  
  Default boot order:
  
   * 0. if keyboard is closed boot automatically attached kernel image
   * 1. try boot from external SD card
   * 2. try boot from internal eMMC memory
   * 3. try boot from attached kernel image
  
  Boot from SD or eMMC in this order:
  
   * 1.
     * 1.1 find boot.scr on first fat partition
     * 1.2 find uImage on first fat parition
     * 1.3 same order for 2. - 4. fat partition
   * 2. same as 1. but for ext2/3 partition
   * 3. same as 1. but for ext4 partition
  
  
  Available additional commands/variables:
  
   * run sercon - Use serial port for control
   * run usbcon - Use usbtty for control
   * run vgacon - Use framebuffer and HW keyboard for control (default)
  
   * run sdboot - Boot from external SD card (see boot order)
   * run emmcboot - Boot from internal eMMC memory (see boot order)
   * run attachboot - Boot attached kernel image (attached to U-Boot binary)
  
   * run scriptload - Load boot script ${mmcscriptfile}
   * run scriptboot - Run loaded boot script
   * run kernload - Load kernel image ${mmckernfile}
   * run initrdload - Load initrd image ${mmcinitrdfile}
   * run kernboot - Boot loaded kernel image
   * run kerninitrdboot - Boot loaded kernel image with loaded initrd image
  
   * run trymmcscriptboot - Try to load and boot script ${mmcscriptfile}
   * run trymmckernboot - Try to load and boot kernel image ${mmckernfile}
   * run trymmckerninitrdboot - Try to load and boot kernel image ${mmckernfile}

  			      with initrd image ${mmcinitrdfile}

  
  Additional variables for loading files from mmc:
  
   * mmc ${mmcnum} (0 - external, 1 - internal)
   * partition number ${mmcpart} (1 - 4)
   * parition type ${mmctype} (fat, ext2)
  
  Additional varuables for booting kernel:
  
   * setup_omap_atag - Add OMAP table into atags structure (needs maemo kernel)
   * setup_console_atag - Enable serial console in OMAP table
   * setup_boot_reason_atag - Change boot reason in OMAP table
   * setup_boot_mode_atag - Change boot mode in OMAP table
  
  USB TTY:
  
   Maemo kernel 2.6.28 will crash if u-boot enable usb tty. So USB TTY is disabled.
   For enabling USB TTY just add this line to file include/configs/nokia_rx51.h
  
   #define CONFIG_USB_TTY
  
  
  ONENAND support:
  
   ONENAND support is disabled because not working yet and cause linux kernel to
   crash or no access to mtd. For enabling ONENAND support add this line at begin
   of file include/configs/nokia_rx51.h
  
   #define ONENAND_SUPPORT
  
  
  UBIFS support:
  
   UBIFS support is disabled, because U-Boot image is too big and cannot be
   flashed with attached zImage to RX-51 kernel nand area. For enabling UBIFS
   support first enable ONENAND support and then add this line at begin of file
   include/configs/nokia_rx51.h
  
   #define UBIFS_SUPPORT