Some udbg questions

[Timur Tabi]

I'm adding udbg support to my console driver, and I've noticed that
there is not much consistency on how the various platforms implement
udbg support.  So I have a few questions:

1. What is the point of implementing udbg_getc?  What does the console
do with any characters it receives this early?
2. In my driver's udbg initialization function, should I be able to
parse the device tree to get parameters?
3. What about command-line parameters?
4. The LPAR and PMAC platforms call register_early_udbg_console (in
the udbg_init_debug_lpar and pmac_init_early functions, respectively),
but none of the other platforms do.  It appears that the other
platforms rely on setup_32.c and setup_64.c to call this function.
What's so special about LPAR and PMAC?
5. Some platforms (like mv64x60) use the ppc_md.init_early function to
initialize the early console.  Others update function
udbg_early_init() in udbg.c instead.  Why do some platforms do it one
way, and other platforms do it the other way?  Which way is preferred?

-- 
Timur Tabi
Linux kernel developer at Freescale