MI boot args revamp?

[Jeff Rizzo <riz%NetBSD.org@localhost>]

I'm only just starting to think of this as a possible reality, but I'd 
like to establish a (better) MI way of passing args to the kernel.  In 
my particular case, I'm interested in passing the root device to the 
kernel from u-boot on several evbarm and evbppc platforms;  I can easily 
see wanting to do the same thing on amd64 sometimes.
Yes, I could go dig up the particular MD way to do it for each case I 
need, but I would really, really like to have a decent MI way to specify 
things, so that when I move from one platform to another, I have to 
re-learn a minimum of stuff.  Also, that I can expect a particular 
NetBSD way of doing things.  I believe the way the current state evolved 
is that originally, there was concern for people expecting the "native" 
platform way of doing things, and adapting NetBSD to it, instead of the 
other way around.  I think we need to change that, however slowly, and 
begin the idea of adapting the platform-specific stuff to NetBSD where 
it makes sense.
I would like to have a way to pass a string composed of the same flags 
(we can continue to use our existing "-a", "-s" and other flags) in a 
consistent manner from one platform to another, to be able to adjust 
driver options, kernel options, whatever, and to be able to expect it to 
be similar whether I'm on amd64, macppc, evbppc, evbarm, or whatever.
Thoughts?  Suggestions for an acceptable approach?

+j