socketcall() is a common kernel entry point for the socket system calls. call determines which socket function to invoke. args points to a block containing the actual arguments, which are passed through to the appropriate call.
User programs should call the appropriate functions by their usual names. Only standard library implementors and kernel hackers need to know about socketcall().
On a some architectures—for example, x86-64 and ARM—there is no socketcall() system call; instead socket(2), accept(2), bind(2), and so on really are implemented as separate system calls.
On x86-32, socketcall() was historically the only entry point for the sockets API. However, starting in Linux 4.3, direct system calls are provided on x86-32 for the sockets API. This facilitates the creation of seccomp(2) filters that filter sockets system calls (for new user-space binaries that are compiled to use the new entry points) and also provides a (very) small performance improvement.