[Ltib] mpc8349emitx.dts device tree entry for pci bridge

[Steve DeLaney]

Hi there, not sure if this is the right forum for this topic but here goes.

We made a kernel update for MPC8349E LTIB to 2.6.25 to support a 
PCI board.  The board is designed as "bridge behind bridge", in other
words there is a PLX PCI bridge chip, behind which lies a vendor chip.  The 
chip enumerates as a bridge, and also asserts INTA in its PCI config PINS.
With the PCI board in the full size slot 1, the scheme is like this:


                 IRQ20
                   ^
mpc8349e pci1      |
------------       |
  plx bridge       |
  ------------   INTA
    vendor chip ---^


The problem we are seeing is the IRQ granted to the board is IRQ 0,
and it appears that the device tree process is unable to process a 
board of this sort (under arch/powerpc/kernel/prom_parse.c) 

As a point of reference we have a success case
on a USB card that does grant INTA on IRQ 20.   But that USB card is
an end node controller device, not a bridge.

We think the best solution to this is probably to add a device tree entry
to describe our more complex PCI bridge board.  
Documentation/powerpc/booting-without-of.txt is a good start but 
its not so obvious how to add such an entry to the device tree.
We were hoping to see if someone could point
us to a example to a similar device tree bridge description? 

Cheers!

/steverino2