A PPA repository exists that deal with being able to use the controls and FN keys of your samsung device.
You can add it by using the command:
sudo add-apt-repository ppa:voria/ppa
Now you need to upgrade your apt cache by using:
sudo apt-get update && sudo apt-get upgrade
Now you can install the 2 packages that give back access to FN keys:
sudo apt-get install samsung-tools
sudo apt-get install samsung-laptop
You can find more information about the Voria packages here:
This only works if your laptop is supported by the kernel. Since these packages use the existing brigthness controls. It only gives you the missing connection between the FN keys and the existing brightness controls. So your laptop must be supported by the kernel.