android/doc: Add socket-api.txt document
android/doc: Add socket-api.txt document

Document describes how socket HAL is working.

pstglia/external-bluetooth-bluez,pstglia/external-bluetooth-bluez,mapfau/bluez,pstglia/external-bluetooth-bluez,pkarasev3/bluez,ComputeCycles/bluez,ComputeCycles/bluez,mapfau/bluez,silent-snowman/bluez,mapfau/bluez,pkarasev3/bluez,ComputeCycles/bluez,ComputeCycles/bluez,silent-snowman/bluez,mapfau/bluez,silent-snowman/bluez,pkarasev3/bluez,pkarasev3/bluez,pstglia/external-bluetooth-bluez,silent-snowman/bluez