DTS configuration of external interrupts on 8347

[Richard Whitlock <richard.whitlo@btconnect.com>]

I have a small problem with a port of linux 2.6.26 to a custom board.
Our board is almost identical to the Analogue & Micro asp 8347 board, so 
I'm using Kumar Gala's excellent fsl tree (thank you Kumar) as it 
already has a defconfig for the asp.
Thanks also to Bryan O'Donoghue for pointing us in the direction of the 
asp port in the first place.

The problem we have is I am unable to request an external interrupt. We 
have an FPGA which has an interrupt line - HW IRQ_0, so thats linux IRQ 48.
I have added the following to the dts file:

fpgaKFAF@0xF8000000 {
                interrupts = <48 8>;
                interrupt-parent = <&ipic>;
}

but whenever I call request_irq() it returns -ENOSYS.

The driver loads fine, and the open function does very little - a call 
to ioremap() - which works, and a call to request_irq() which does not.
Is there anything else I have to do to configure this interrupt?

Regards,

Richard.