BSP instructions

[Mathew Benson]

I finally found the time to start playing with RTEMS.  I'm a flight
software engineer, but have never written a BSP from scratch.  I've
only tweaked existing ones.  I have a Raspberry Pi B and would like to
use that as my test bed.  Raspberry Pi is ARM based.  It appears the
generic RTEMS ARM BSP is deprecated and has been removed.  Two
questions.  First, is there a tutorial, wiki, or some sort of
documentation on how to create a BSP?  Second, which BSP should I
start with?