Re: Changes to gt64260 interrupt support code

The ppc64 port has an array of virtual irq's which is used to index to
the real irq.  In the interests of easy debugging (eg when drivers print
out their irq number) the virtual irq is kept identical to the actual
whenever possible.

arch/ppc64/prom.c sets up the map (virt_irq_to_real_map), and
arch/ppc64/xics.c (the interrupt controller) uses it.

Simple translation of irqs doesn't really solve the
problem; a general solution would provide us with the
ability to initialize and service interrupt requests
routed through multiple, nested, heterogeneous
controllers no matter what the HW designers were
smoking when they laid out the system.  See earlier
posts to this list for good discussion on this topic.


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