The chip level hardware descriptor structure irq_chip contains all the direct chip relevant functions, which can be utilized by the irq flow implementations.
ack()
mask_ack() - Optional, recommended for performance
mask()
unmask()
retrigger() - Optional
set_type() - Optional
set_wake() - Optional
These primitives are strictly intended to mean what they say: ack means ACK, masking means masking of an IRQ line, etc. It is up to the flow handler(s) to use these basic units of lowlevel functionality.