howto add external built kernel modules to an image?

[Steffen Sledz <sledz@dresearch.de>]

I'd like to build a kernel module (let's say it's named drpnx) outside
the kernel sources and add the resulting drpnx.ko to an rootfs image.

I created a bitbake recipe using
recipes/minifo/minifo-modules_0.6.1-pre1.bb as a sample and i'm able
to bitbake this recipe using the -b option.

But now i'm out of ideas. How to add drpnx.ko to a rootfs image? I tried

IMAGE_INSTALL += " drpnx "
IMAGE_INSTALL += " kernel-module-drpnx "
IMAGE_INSTALL += " drpnx-module "

but none of them worked. :(

What's the right way to do this?

Steffen