powerpc: 32BIT vs. 64BIT (PPC32 vs. PPC64)

Hi,

Is there a good way (or a shortcut) to do something like:

$ make ARCH=powerpc O=PPC32 [other_options] allmodconfig
  to get a PPC32/32BIT allmodconfig

and also be able to do:

$make ARCH=powerpc O=PPC64 [other_options] allmodconfig
  to get a PPC64/64BIT allmodconfig?


Note that arch/x86, arch/sh, and arch/sparc have ways to do
some flavor(s) of this (from Documentation/kbuild/kbuild.txt;
sh and sparc based on a recent "fix" patch from me):

x86: i386 for 32 bit, x86_64 for 64 bit
sh: sh for 32 bit, sh64 for 64 bit
sparc: sparc32 for 32 bit, sparc64 for 64 bit


thanks,
-- 
~Randy