Xiaomi's devices run a custom Android overlay called MIUI, which uses its own battery-saving solution in most cases, but users that are willing to root their device can use the stock Doze feature built into Android 6.0 (Marshmallow) and above. XDA Developers forum user asusm930 has developed a simple solution that enables the feature on MIUI devices that don't already have it enabled. The fix involves implanting a modified framework-res.apk file into your system directory, which is where the rooting requirement comes in. Once this file is in place, a quick reboot of the device will enable the feature, delivering battery life savings while the screen is off.
The trick works because a value in the framework-res file defines whether Doze is on or off. That value is simple enough to modify by replacing the file with a modified copy, but cannot be modified live because it requires decompiling the APK file. Before undertaking the procedure, you can check if you're already using Android's Doze method instead of Xiaomi's by checking for "Doze Idle Stat" in the Better Battery Stats app. If you do not have that value or it is at zero, then your device is using the MIUI power-saving implementation, and may benefit from using the fix to get Android's Doze version working. This fix should work on just about every recent MIUI device, but may require some tweaks to the file for some devices.
Another option, for those who encounter bootloops or don't want to mess about with system files, is to use the L Speed app. This solution still requires root, and can force an aggressive or light dozing mode, but cannot enable Google's Doze implementation along with all of its built-in checks and balances. The built-in MIUI solution does a fine job according to users, which means that the device in question may get better battery life with the fix, or may find that the MIUI version works better; it's recommended to take a backup in recovery before doing this to be sure, and of course, it should go without saying that you should definitely back up your old framework-res.apk in case anything goes wrong.