U-Boot Development for customization on router

Hi All,

I have some basic working experience with u-boot but don't have complete understanding.

I have to customize u-boot of a router and i want to know how to start ??

what hardware are necessary like serial, JTAG etc ??

Thanks in advance

You can get a USB TTL adapter for about a dollar from ebay. Like this Amazon.com: Qunqi CP2102 Module STC Download Cable USB 2.0 to TTL 5PIN Serial Converter: Computers & Accessories. Serial pin out info can be found for most models on the openwrt wiki. Look for debricking guides.
Also see pepe2k/u-boot_mod and Breed uboot

i have enabled the serial console.

But my question was for a new board that is not yet suppported !!

How to do changes in uboot ?

How to change the flash layout .. especially size ??

How to install uboot in case i crash uboot ??

Debricking is for supported hardware .. i am talking about new hardware that is not supported .

Thanks in advance.