There is an example of LTE netdevice in the Linux source tree?

In particular, I would like to know if there is any device driver that implements the layers required by the 3GPP standard. I imagine that it should exist something since Android is communicating over LTE, but I can't find any reference. What I fear more is that everything related to LTE is inside the closed device firmware, and data is sent from the TC layer into this black-box firmware through a sort of API. In this case, it would be wonderful to know where, exactly, this API is used, to try to understand what the firmware is doing.

Thank you!!