unit: link up getty configuration from man page and unit files

man/systemd-getty-generator.xml

@@ -77,6 +77,12 @@
                 implements the <ulink
                 url="http://www.freedesktop.org/wiki/Software/systemd/Generators">generator
                 specification</ulink>.</para>
+
+                <para>Further information about configuration of
+                gettys you may find in <ulink
+                url="http://0pointer.de/blog/projects/serial-console.html">systemd
+                for Administrators, Part XVI: Gettys on Serial
+                Consoles (and Elsewhere)</ulink>.</para>
         </refsect1>
 
         <refsect1>

units/getty.target

@@ -7,4 +7,5 @@
 
 [Unit]
 Description=Login Prompts
-Documentation=man:systemd.special(7)
+Documentation=man:systemd.special(7) man:systemd-getty-generator(8)
+Documentation=http://0pointer.de/blog/projects/serial-console.html

units/getty@.service.m4

@@ -7,7 +7,8 @@
 
 [Unit]
 Description=Getty on %I
-Documentation=man:agetty(8)
+Documentation=man:agetty(8) man:systemd-getty-generator(8)
+Documentation=http://0pointer.de/blog/projects/serial-console.html
 After=systemd-user-sessions.service plymouth-quit-wait.service
 m4_ifdef(`TARGET_FEDORA',
 After=rc-local.service

units/serial-getty@.service.m4

@@ -8,6 +8,7 @@
 [Unit]
 Description=Serial Getty on %I
 Documentation=man:agetty(8) man:systemd-getty-generator(8)
+Documentation=http://0pointer.de/blog/projects/serial-console.html
 BindsTo=dev-%i.device
 After=dev-%i.device systemd-user-sessions.service plymouth-quit-wait.service
 m4_ifdef(`TARGET_FEDORA',