External int in dts

[Sean MacLennan]

I have an FPGA which uses external int 1, which is interrupt 24 on UIC0. 
I tried the following entry in various places:

        FPGA0: fpga {
            compatible = "pika,fpga";
            interrupts = <18 4>;
            interrupt-parent = <&UIC0>;
        };

Any hints, or is this the wrong way to enable an external int?

Cheers,
   Sean