This adds irqnest test to trigger TESTIRQ_LO, which will in
turn trigger TESTIRQ_HI to show nested IRQ feature. The results
can be observed by `cat /proc/irqs`. The app also contains a
kernel module for testing ISRs. So a successful build has two
artifacts, the pass1/ko/irqnest.ko and the irqnest command.
To use the app, first install the kernel module via `insmod`
command, then run `irqnest` to trigger test IRQs, then use
`irqinfo` to see the results.
Though checked with rv-virt:nest-pnsh and rv-virt:nest, this
is not limited to RiscV platform.
Signed-off-by: Yanfeng Liu <p-liuyanfeng9@xiaomi.com>
anjiahao