Our IRQ storm detection works when an interrupt handler returns
IRQ_NONE for thousands of consecutive interrupts in a second. It
doesn't hurt to occasionally return IRQ_NONE when the interrupt is
actually genuine.

Drivers should only be returning IRQ_HANDLED if they have actually
*done* something to stop an interrupt from happening — it doesn't just
mean "this really *was* my device".
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>
Cc: davem@davemloft.net
Link: http://lkml.kernel.org/r/1446016471.3405.201.camel@infradead.orgSigned-off-by: NThomas Gleixner <tglx@linutronix.de>