Before Fedora 21 I had modified the following variable GRUB_CMDLINE_LINUX in the default grub file: /etc/default/grub in order to append `acpi_backlight=vendor`
#emacs /etc/default/grub GRUB_CMDLINE_LINUX="...existing vars here... acpi_backlight=vendor"
After the upgrade I had to change this from acpi_backlight=vendor to acpi_backlight=intel. Once the file is updated run:
#grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
Once done, reboot and the screen brightness controls should work however the screen brightness range goes from 0 to 4882 (/sys/class/backlight/intel_backlight/max_brightness) instead of around 100 to 4882 so if you dim the brightness all the way down, your screen will be completely black.