Writing GCC for processor

["Bansidhar Arvind Deshpande - CTD, Chennai." <bansidhara@xxxxxxxxxxxxxxx>]

Hi GCC gurus,

Please tell me the steps involved to write GCC(and rest tool chain) for a
processor which is not supported by GCC . 
At least provide me URLs for the documentation on same.

Thanking you 

Bansidhar