Interrupt handling on SMP system

Hi all,
  I had a few question regarding how interrupt handling work on linux
within a SMP systems.

1. Which processor gets the interrupt when a new packet arrives? Is
there any policy mechanism which can guide the interrupt to the idle
processor etc? Do the processors share an interrupt line and an
interrupt controller assign it to a specific processor?

2. When a soft IRQ is scheduled by the driver and picked up by a
ksoftirqd thread, does it get processed entirely on the same
processor? Does ksoftirqd/i thread processes the packets in the ith
processor queue only?

Regards,
Majid