I have completed an UEFI installation of Linux Mint 17.3 onto another partition on my OS X boot SSD.
It is working very well, so far.
As WonkeyDonkey stated, the Linux Mint installer places another folder (named 'ubuntu') into the EFI partition alongside the Clover stuff that's already there.
After installation, the system's Boot order will be reset so that your 1st Boot Device is 'ubuntu' and the system will boot straight into Linux instead of Clover. To get Clover instead, enter Setup and reset your 1st Boot device to whichever one is Clover. To ensure it stays that way, I disabled 2nd and 3rd boot device to prevent ubuntu or Windows from 'taking over'.
When installing, it's important to place the GRUB bootloader onto the partition with your EFI. The default location for GRUB is /dev/sda. My EFI was located on /dev/sda1, so that is what I selected.
One more thing worth mentioning (mabye): To minimize the potential for problems, I did all of my pre-installation partitioning in OS X using Disk Utility. That is, I created a second volume intended for Linux, and formatted that new volume Mac OS Extended Journaled (I did not use FAT32, because Going Bald mentioned earlier not to do this when installing Linux UEFI). The newly-created volume is then reformatted EXT4 by the Linux Live installer. Using DU to do the pre-install partitioning also creates the 128MB gap between volumes. Since DU likes to have that gap, then I prefer to have it there.
I use Disk Utility to do all of this preliminary disk partitioning work, because I don't know how things would work out if I used Gparted to shrink the OS X volume. Best to resize OS X using a native OS X app, I think.
To recap: My system is now triple-boot with OS X and Linux Mint installed on separate volumes on the same SSD, and Windows 10 installed on a second hard drive. All three operating systems are EFI and bootable with Clover.
I hope that this is informative for someone.