When you apply a device package to enable new device support, a cluster-wide reboot is not required for Cisco Unified Communications Manager version 11.5(1) or later. Instead, after you add the device pack, do the following in Cisco Unified Communications Manager:
If you are using Cisco Unified Communications Manager version 11.0(1) or earlier, a cluster-wide reboot is required. A cluster-wide reboot is not required when you apply a device package to update existing firmware or configuration.
Reference:
https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/compat/matrix/CMDP_BK_CCBDA741_00_cucm-device-package-compatibility-matrix/CMDP_BK_CCBDA741_00_cucm-device-package-compatibility-matrix_chapter_00.html