How to separate a device IRQ?
 

i.e. make it use its own IRQ and not use the IRQ that's already used by
other device. IOTW, prevent IRQ sharing or used shared IRQ.

I have my display adapter device IRQ shared with the motherboard PCI-to-USB
host controller device, and I want the display adapter device use its own
unshared IRQ.

Currently, both devices use IRQ 20 (second core of dual-core CPU). The
unused IRQs in my system are 2, 3, 5, 6, 7, 10, 16, 17, and 19; as seen from
the Device Manager using "Resources by type" view.