If you’re wondering what’s new in Linux kernel 4.4.21 LTS that makes it such a big update, we can tell you that the major part of the patch is occupied by updated drivers, in particular for GPU (mostly Intel i915 and Radeon), Bluetooth, CPUFreq, Crypto, HV, InfiniBand, IRQ Chip, LightNVM, MD, MMC, NVMe, Pulse Width Modulation (PWM), s390, SCSI, VHost, and networking, lots and lots of Ethernet networking drivers. There are also various improvements to the EXT4, OverlayFS, UBIFS, and XFS filesystems, an updated sound stack with Firewire enhancements, and updated networking stack with IPv4, IPv6, Netfilter, Reliable Datagram Sockets (RDS), and Transparent Inter-process Communication (TIPC) changes, as well as multiple core kernel fixes.