Samsung GALAXY S6 EDGE User Manual page 285

Allow Exceptions
This option lets you customize which notifications are allowed while your device is in Do not disturb mode.
1. From home, tap Apps
2. Tap Sounds and vibration
3. Tap Do not disturb.
4. Tap Allow exceptions, and then tap one of the following options:

No exceptions: Allow no exceptions.

Alarms only: Allow exceptions for alarms.

Custom: Set your own exceptions.
Settings
> Settings .
.
274