IBM T23 volume keys handling

[Michał Frynas]

Hello,

can someone of you guys, point me a place within the kernel sources, where
the volume up/volume down keys are handled?
In more specific I'd like to find a place where the volume keys press event
is being handled, and add there something like this:

devctl_notify("ACPI_CUSTOM", "ACPI_VOLUME", (arg > val) ? "ACPI Volume Up" :
"ACPI Volume Down", NULL);

Thanks in advance,
Michal Frynas.