[U-Boot] Default boot arguments in case of missing FDT

[Udit agarwal]

Hi all,
I need to implement a check on whether user provided a valid FDT or not(on
beagle bone Black).
So,

   - First, what is the default value(if any) of FDT pointer passed on via
   uboot to kernel?
   - Is there a option to set/customize the default FDT pointer value?

Regard,

Udit agarwal