How do I build the iptables kernel module for a loaded kernel?

view full story

http://unix.stackexchange.com – I've built a kernel with loadable module support for various reasons, one of them the possibility to compile modules and load them without rebooting. This is supposed to be useful when I need a module that I had not enabled in the kernel config. Now, with drivers like nouveau, it's as easy as going to the source directory, and running make M=drivers/gpu/drm/nouveau. How can I build an updated iptables module without compiling a whole kernel and rebooting? Is it even possible? (HowTos)