system_data_types.7: Document siginfo_t

Note: There are a few members of this structure that are
not required by POSIX (XSI extensions, and such).

I simply chose to not document them at all.

Signed-off-by: Alejandro Colomar <colomar.6.4.3@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man7/system_data_types.7

@@ -213,6 +213,39 @@ See also:
 See also the
 .I aiocb
 structure in this page.
+.\"------------------------------------- siginfo_t --------------------/
+.TP
+.I siginfo_t
+.IP
+Include:
+.IR <signal.h> ;
+or
+.IR <sys/wait.h> .
+.IP
+.EX
+typedef struct {
+    int             si_signo; /* Signal number */
+    int             si_code; /* Signal code */
+
+    pid_t           si_pid; /* Sending process ID */
+    uid_t           si_uid; /* Real user ID of sending process */
+    void           *si_addr; /* Address of faulting instruction */
+    int             si_status; /* Exit value or signal */
+
+    union sigval    si_value; /* Signal value */
+} siginfo_t;
+.EE
+.\".IP
+.\" FIXME: Add a description?
+.IP
+Conforming to: POSIX.1-2001 and later.
+.IP
+See also:
+.BR pidfd_send_signal (2),
+.BR rt_sigqueueinfo (2),
+.BR sigaction (2),
+.BR sigwaitinfo (2),
+.BR psiginfo (3)
 .\"------------------------------------- sigval -----------------------/
 .TP
 .I sigval
@@ -239,9 +272,9 @@ See also:
 See also the
 .I sigevent
 structure
-.\"and the
-.\".I siginfo_t	FIXME
-.\"type
+and the
+.I siginfo_t
+type
 in this page.
 .\"------------------------------------- size_t -----------------------/
 .TP