Awesome
LineageOS Source Device Tree Template
Start your Android career here. Build device trees and port custom ROMs and recoveries to new devices easily with this template.
Study the templates included to understand the file scheme, and then extract a boot or recovery image from your device, and run the mkvendor.sh script to make a preliminary tree. Here is Google's AOSP tutorial on how to make a device tree and another good explanation on StackOverflow on what these files do.
You will need to add extra info (e.g. TARGET_BOARD_PLATFORM in BoardConfig.mk) before it is usable.
Last of all, have fun! Do some wonderful things with Android :)
Make sure to cross-reference information shown in tutorials you find with other device trees in the LineageOS repositories, making sure not to add deprecated properties or the like into your files, as the tutorials may be old.
You can build TWRP (custom recovery) with your device trees. The official compilation tutorial can be found here (tutorial by @Dees-Troy on XDA).