This means you can now finally log not only to stderr of the running process, but also configure any number of log files (each with its own log categories/levels) and through syslog.
In addition, all of the settings can now be configured from the vty (and persistently in the configuration file). You can also re-configure the log levels for those files (and stderr!) at runtime.
Please see the following new commands on the vty:
log file FILENAME log syslog log stderr no log (syslog|stderr) no log file FILENAME
Within each of those log vty nodes, you can then use the familiar commands like 'logging level mm debug' or 'log filter all 1' in order to configure which subsystems should log with what level of verbosity to the given target.
The abovementioned logging support is immediately available to all Osmocom programs, including osmo-nitb, osmo-bsc, gb_proxy, osmo-sgsn, bsc_nat and many others.