Apple announced that in a news report. Once the update is installed, iPhone owners can simply press the Pair button on the Xbox controller to pair the controller with their phone.
DualSense users must press the Share and PlayStation button simultaneously until the light on the controller starts to flash to connect both devices. Once this action is done, the controller will appear under bluetooth devices on your phone. The same applies to Xbox controllers, by the way.
The 14.5 update also introduces all kinds of other features, such as the ability to use Iphones unlock via Apple Watch. You can read all about this in the news item of the tech giant.