The kernel source code for a device is a great thing for developers and those that like to tinker with their device. More and more manufacturers are starting to get on the proverbial bandwagon and have been doing a fairly great job at keeping the kernel codes for their devices out and available. Many have even been right on point to have them available right after an update goes out or when a new device is physically available for purchase. Sony has done just that. Just yesterday the Xperia Z1s became available for customers at physical T-Mobile stores. At the same time, Sony released the kernel code for that very device.
Go get your download on if you would like to though. You can pick up the 347MB file over at Developer.SonyMobile.
Source: Sony Mobile Via Android Police