sched/waitpid: rename nx_waitpid() to nxsched_waitpid()

Signed-off-by: chao an <anchao@xiaomi.com>

include/nuttx/sched.h

@@ -1359,11 +1359,53 @@ int nxsched_set_affinity(pid_t pid, size_t cpusetsize,
 int nxsched_get_stackinfo(pid_t pid, FAR struct stackinfo_s *stackinfo);
 
 /****************************************************************************
- * Name: nx_wait/nx_waitid/nx_waitpid
+ * Name: nxsched_waitpid
+ *
+ * Description:
+ *   This functions will obtain status information pertaining to one
+ *   of the caller's child processes. This function will suspend
+ *   execution of the calling thread until status information for one of the
+ *   terminated child processes of the calling process is available, or until
+ *   delivery of a signal whose action is either to execute a signal-catching
+ *   function or to terminate the process. If more than one thread is
+ *   suspended in nxsched_waitpid() awaiting termination of the same process,
+ *   exactly one thread will return the process status at the time of the
+ *   target process termination. If status information is available prior to
+ *   the call to nxsched_waitpid(), return will be immediate.
+ *
+ * Input Parameters:
+ *   pid - The task ID of the thread to waid for
+ *   stat_loc - The location to return the exit status
+ *   options - ignored
+ *
+ * Returned Value:
+ *   If nxsched_waitpid() returns because the status of a child process is
+ *   available, it will return a value equal to the process ID of the child
+ *   process for which status is reported.
+ *
+ *   If nxsched_waitpid() returns due to the delivery of a signal to the
+ *   calling process, -1 will be returned and errno set to EINTR.
+ *
+ *   If nxsched_waitpid() was invoked with WNOHANG set in options, it has
+ *   at least one child process specified by pid for which status is not
+ *   available, and status is not available for any process specified by
+ *   pid, 0 is returned.
+ *
+ *   Otherwise, (pid_t)-1 will be returned, and errno set to indicate the
+ *   error:
+ *
+ *   ECHILD - The process specified by pid does not exist or is not a child
+ *            of the calling process, or the process group specified by pid
+ *            does not exist does not have any member process that is a child
+ *            of the calling process.
+ *   EINTR - The function was interrupted by a signal. The value of the
+ *           location pointed to by stat_loc is undefined.
+ *   EINVAL - The options argument is not valid.
+ *
  ****************************************************************************/
 
 #ifdef CONFIG_SCHED_WAITPID
-pid_t nx_waitpid(pid_t pid, FAR int *stat_loc, int options);
+pid_t nxsched_waitpid(pid_t pid, FAR int *stat_loc, int options);
 #endif
 
 #undef EXTERN