Let me humbly suggest that the kernel source code be organized much like
the sun3 kernel source when we ran into this same problem.  I would
suggest:

arch/arm32/arm32    Common arm32 code (string routines and the like)
arch/arm32/dnard    Code for the DNARD port
arch/arm32/cats     Code for the CATS ports
arch/arm32/riscpc   ...
arch/arm32/ebsa285  ...
arch/arm32/conf/GENERIC_DNARD
arch/arm32/conf/GENERIC_CATS
arch/arm32/conf/GENERIC_RISCPC

-J