Hi Konstantin,
the IRQ are usually freely configurable via the LDN. Using the lower bits of 0x70h is quite common to select the IRQ.
The SuperIO is connected via LPC, which supports all legacy IRQs by Serial-IRQ. Further, depending on the Chipset, it must allow to receive the IRQs over the SerIRQ line of the LPC.
Best Regards, lynxis