system_data_types.7: Add 'struct sockaddr'

Signed-off-by: Alejandro Colomar <alx.manpages@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man7/system_data_types.7

@@ -1226,6 +1226,31 @@ and
 .I ssize_t
 types in this page.
 .RE
+.\"------------------------------------- sockaddr ---------------------/
+.TP
+.I sockaddr
+.RS
+.IR Include :
+.IR <sys/socket.h> .
+.PP
+.EX
+struct sockaddr {
+    sa_family_t sa_family; /* Address family */
+    char        sa_data[]; /* Socket address */
+};
+.EE
+.PP
+Describes a socket address.
+.PP
+.IR "Conforming to" :
+POSIX.1-2001 and later.
+.PP
+.IR "See also" :
+.BR accept (2),
+.BR getpeername (2),
+.BR getsockname (2),
+.BR socket (2)
+.RE
 .\"------------------------------------- ssize_t ----------------------/
 .TP
 .I ssize_t