Comment 15 for bug 429351

To enable the FN keys, you need to edit the file '/lib/udev/rules.d/95-keymap.rules', search for the string 'NC10', then add your model to the list of Samsung models.

In other words, modify the line:
ENV{DMI_VENDOR}=="[sS][aA][mM][sS][uU][nN][gG]*", ATTR{[dmi/id]product_name}=="*NC10*|*NC20*|*SP55S*|..."
in:
ENV{DMI_VENDOR}=="[sS][aA][mM][sS][uU][nN][gG]*", ATTR{[dmi/id]product_name}=="*NC10*|*NC20*|*N120*|*SP55S*|..."

If after a reboot you notice that some FN keys are stucked and don't get released after they are used, this means the kernel needs to be patched for proper support, like for other Samsung models.
Let me know if this is the case: since I'm already building a patched kernel for other models, I can easily add support for the N120 too.