Question about GPIO as interrupt source

[Stefan Wahren]

Hi,

i want to define a GPIO (GPIO23 in my example) as an interrupt source 
for a SPI device node. I've looked at [1], but after all i still do not 
known how to define the interrupts property. I know the property must 
have 2 cells.

I don't have a clue, how the mapping between interrupt and GPIO work on 
the Raspberry Pi.

Best regards
Stefan Wahren

[1] - 
http://lxr.free-electrons.com/source/Documentation/devicetree/bindings/interrupt-controller/brcm,bcm2835-armctrl-ic.txt