Managing the device tree data in U-Boot
				 =======================================

The 'fdt' command can be used to manipulate the device tree (DT) data
that is passed from U-Boot to Linux.

- 'fdt boardsetup' will trim out some device nodes according to
  environment settings:

Environment setting		removed nodes
otg_mode=host			usbh1
otg_mode=device			usbotg
otg_mode=<UNSET>		<both of the above> + usbphy

touchpanel=edt-ft5x06		ti,tsc2007
touchpanel=tsc2007		edt,edt-ft5x06
touchpanel=<UNSET>		<both of the above>

Note: This command is automatically executed when booting Linux via
      the 'bootm_cmd' environment variable.

- 'fdt rm' and 'fdt add' can be used to remove/create additional nodes

The whole DT data can be saved to and reloaded from the 'dtb' (or any
other) partition:
  nand erase.part dtb
  nand write.jffs2 ${fdtcontroladdr} dtb

Note: To prevent U-Boot from overwriting data in the succeeding
partition when encountering bad blocks in the 'dtb' partition, it is
wise to explicitly specify the write size according to 'totalsize'
displayed by the command 'fdt header':
TX53 U-Boot > fdt header
magic:                  0xd00dfeed
totalsize:              0x3f9e (16286)
off_dt_struct:          0x78
off_dt_strings:         0x2bb8
off_mem_rsvmap:         0x28
version:                17
last_comp_version:      16
boot_cpuid_phys:        0x0
size_dt_strings:        0x3e6
size_dt_struct:         0x2b40
number mem_rsv:         0x0
TX53 U-Boot > nand write.jffs2 ${fdtcontroladdr} dtb 3f9e

If a DT is loaded from flash which should not be further manipulated
upon booting Linux, the string 'fdt boardsetup;' should be removed
from the 'bootm_cmd' environment variable.

Loading the DT data:
  nand read ${fdtcontroladdr} dtb