[uml-user] New IRQ support

[Ricardo N. <ric...@gm...>]

I've already made that question a few weeks ago but I couldn't make it work.

So, in order to support new IRQs I understand that we need to follow those
steps:


   1. Add the IRQ IDs to /kernel/arch/um/include/asm/irq.h, or at least
   change LAST_IRQ macro value to the bigger IRQ ID;
   2. Create one file per IRQ: is that a host or UML file? I'm trying to
   follow random driver example but /dev/random exists in both;
   3. When I need to throw an IRQ I just have to write something on the
   file and send a SIGIO signal. Which process needs to receive the SIGIO?


In my system I'm using the original driver and using a userspace
application to emulate the hardware (communication through netlink
sockets). So, the emulator decides when IRQs needs to be launched and, at
the moment, communicates that to the kernel driver.