Document, that PROCESS of signal-process can be a string

* doc/lispref/processes.texi (Signals to Processes) [signal-process]:
* src/process.c (Fsignal_process): Document, that PROCESS can be a
string.

doc/lispref/processes.texi

@@ -1497,6 +1497,9 @@ If @var{process} is a process object which contains the property
 @code{remote-pid}, or @var{process} is a number and @var{remote} is a
 remote file name, @var{process} is interpreted as process on the
 respective remote host, which will be the process to signal.
+
+If @var{process} is a string, it is interpreted as process object with
+the respective process name, or as a number.
 @end deffn
 
 Sometimes, it is necessary to send a signal to a non-local

src/process.c

@@ -7185,6 +7185,8 @@ If PROCESS is a process object which contains the property
 `remote-pid', or PROCESS is a number and REMOTE is a remote file name,
 PROCESS is interpreted as process on the respective remote host, which
 will be the process to signal.
+If PROCESS is a string, it is interpreted as process object with the
+respective process name, or as a number.
 SIGCODE may be an integer, or a symbol whose name is a signal name.  */)
   (Lisp_Object process, Lisp_Object sigcode, Lisp_Object remote)
 {