Here is a list of all documented namespaces with brief descriptions:

[detail level 123]

N__cxxabiv1 [external]
N__gnu_cxx [external]
N__gnu_debug [external]
N__gnu_internal [external]
N__gnu_parallel [external]
N__gnu_pbds [external]
N__gnu_sequential [external]
Nabi [external]
Ndetail [external]
▼Nepics	Copyright - See the COPYRIGHT that is included with this distribution
Ndebug [external]
NpvAccess	Holds all PVA related
NpvData [external]
Npvac	See Client API API
Npvas	See Server API API
Nsimd_abi [external]
Nstd [external]