Documentation for spatial SQL public preview - Where is it?

Lucas_N
New Contributor II

Hi everybody,
since DBR 17.1 spatial sql functions (st_point(), st_distancesphere, ... ) are in public preview.
The functionality is presented in this talk Geospatial Insights With Databricks SQL: Techniques and Applications or discussed here in the forum Spatial Queries - Databricks Community - 69259

However I am unable to find the documentation regarding these functions. I tried googeling all key word variants but no luck.
Can someone please point me in the right direction?
Thank you!