I have not tried to manipulate the GP LED, if I find a document about it or if I'm able to manage it I will let you know, also here is a GPIO programing tutorial that you might find useful to handle the GPIO from Linux.
Intel Galileo - Programming GPIO From Linux
Yes, I figured out how to poke at the gpio's mentioned by Sergey.
What I want to do is like described here: http://www.armadeus.com/wiki/index.php?title=GPIO_LEDS
I'm wondering if ./linux/drivers/gpio/gpio-sch.c could be a good place to put in the platform_led structure...
All the examples I can find seems to point to some kind of board setup.c file,
but I haven't been able to spot one for the Galileo. Any pointers would be most welcome!