An Android kernel is a mainstream Linux kernel, with additional drivers for the specific device, and other additional functionality, such as enhanced power management and faster graphics support.
Many features in the Android kernel are later added to upstream Linux after the open-source community has accepted.
When compared to Linux kernel, the Android common kernel has 355 changes, 32266 insertions, and 1546 deletions (as of February 2018).
Android kernel is more popular and has more footprints compared to linux kernel which leads to more support world-wide
SOC vendor supporting android kernel doesn’t need to work to provide linux kernel support to bring in RDKV stack.