The idea is that the basic extension resides inside the the normal
recipe directories. Depending on the version of poky the bbappends
need to be included. Appends applying to all versions will be put
into the shared folder, specific ones into the specific directory.
Once a bbappend can not be shared anymore it needs to be copied.
RevB and RevC feature different kind of nand flash. RevB is still
pre-production hardware so for the few units allow to set the right
flash parameters in the local.conf.