rtems: Add rtems_clock_get_uptime_seconds()

doc/user/clock.t

@@ -23,6 +23,7 @@ the clock manager are:
 @item @code{@value{DIRPREFIX}clock_get_ticks_since_boot} - Get ticks since boot
 @item @code{@value{DIRPREFIX}clock_get_uptime} - Get time since boot
 @item @code{@value{DIRPREFIX}clock_get_uptime_timeval} - Get time since boot in timeval format
+@item @code{@value{DIRPREFIX}clock_get_uptime_seconds} - Get seconds since boot
 @item @code{@value{DIRPREFIX}clock_set_nanoseconds_extension} - Install the nanoseconds since last tick handler
 @item @code{@value{DIRPREFIX}clock_tick} - Announce a clock tick
 @end itemize
@@ -701,6 +702,36 @@ call.
 
 This directive may be called from an ISR.
 
+@c
+@c
+@c
+@page
+@subsection CLOCK_GET_UPTIME_SECONDS - Get the seconds since boot
+
+@cindex clock get uptime
+@cindex uptime
+
+@subheading CALLING SEQUENCE:
+
+@ifset is-C
+@findex rtems_clock_get_uptime_seconds
+@example
+time_t rtems_clock_get_uptime_seconds(void);
+@end example
+@end ifset
+
+@subheading DIRECTIVE STATUS CODES:
+
+The system uptime in seconds.
+
+@subheading DESCRIPTION:
+
+This directive returns the seconds since the system was booted.
+
+@subheading NOTES:
+
+This directive may be called from an ISR.
+
 @c
 @c
 @c