"root=/dev/mtblock3" or "root=dev/mtddblock/3"

Hello,

could anybody explain me the difference between this two commands.
I want to boot the RFS out of the NAND Flash Partition 3 and tell the kernel this through the bootargs.

This works:

"root=dev/mtddblock/3" works,

but in many examples is shown that this should be added to the bootargs...?

"root=/dev/mtblock3"

The scond one doen?t work at my system ??? Why?

Thank you

Best regards 

Manuel Sahm