CosmOS routes all interrupts via /interrupts/interrupt_router.h.
The ISR's in interrupts/irq.c all route to routeInterrupt which is defined in /interrupts/interrupt_router.h
/interrupts/interrupt_router.h provides the function void interrupt_router_register_interrupt_handler(int interruptNumber, interrupt_handler func); which devices can use to establish a subscription to an interrupt.
The function prototype typedef void (*interrupt_handler)(stack_frame *frame); must be implemented by devices wishing to subscribe to an interrupt.