uio irq handling outline

#include "uio-irq.h"  // https://pastebin.com/w42Ti0Hz

// blocking, for level-triggered interrupts:
int fd = open( path, O_RDWR | O_CLOEXEC );
setup_irq();
loop {
    uio_irqenable( fd );
    uio_wfi( fd );
    handle_irq();
}

// blocking, for edge-triggered interrupts:
int fd = open( path, O_RDWR | O_CLOEXEC );
setup_irq();
loop {
    uio_irqenable( fd );
    handle_irq();
    uio_wfi( fd );
}


// non-blocking, for level-triggered interrupts:
int fd = open( path, O_RDWR | O_CLOEXEC | O_NONBLOCK );
setup_irq();
uio_irqenable( fd );
when fd readable {
    uio_wfi( fd );
    handle_irq();
    uio_irqenable( fd );
}

// non-blocking, for edge-triggered interrupts:
int fd = open( path, O_RDWR | O_CLOEXEC | O_NONBLOCK );
setup_irq();
uio_irqenable( fd );
handle_irq();
when fd readable {
    uio_wfi( fd );
    uio_irqenable( fd );
    handle_irq();
}