There's a closed pull request on the void-packages repository

pinebookpro-kernel: overclock patch
https://github.com/void-linux/void-packages/pull/28007

Description:
Pinebook PRO uses the same OP1 RK3399 of many other chromebooks devices. 
These devices has been rated for 2.1Ghz max clock speed.
Use the OP1 profile already present in the kernel tree.

@ericonr @CameronNemo