handle multiple BTSs with one PCU
OsmoPCU has been used so far in BTS co-located scenario only. This scenario always consists of exactly one BTS instance and exactly one PCU instance. When the PCU is used on a BSC colocated scenario one PCU may serve multiple BTSs. OsmoPCU already manages a list with BTSs and the PCU socket protocol already supports multiple BTSs as well but it is unclear how mature this is. At least the code/API that is used to handle the direct PHY access is not able to distinguish between different BTSs.