Relocate docs/ --> doc/, like most other projects have

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

doc/plugins.md

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+Hooks & Plugins
+===============
+
+* [Plugins](#plugins)
+* [Hooks](#hooks)
+  * [Bootstrap Hooks](#bootstrap-hooks)
+  * [Runtime Hooks](#runtime-hooks)
+  * [Shutdown Hooks](#shutdown-hooks)
+
+Finit can be extended to add general functionality in the form of I/O
+monitors, built-in inetd services, or hook plugins.
+
+The following sections detail existing plugins and hook points.  For
+more information, see the plugins listed below.
+
+
+Plugins
+-------
+
+For your convenience a set of *optional* plugins are available:
+
+* *alsa-utils.so*: Restore and save ALSA sound settings on
+  startup/shutdown.  _Optional plugin._
+
+* *bootmisc.so*: Setup necessary files and system directories for, e.g.,
+  UTMP (tracks logins at boot).  This plugin is central to get a working
+  system and runs at `HOOK_BASEFS_UP`.  The `/var`, `/run`, and `/dev`
+  file systems must be writable for this plugin to work.
+
+  Note: On an embedded system both `/var` and `/run` can be `tmpfs` RAM
+  disks and `/dev` is usually a `devtmpfs`.  This must be defined in the
+  `/etc/fstab` file and in the Linux kernel config.
+
+* *dbus.so*: Setup and start system message bus, D-Bus, at boot.
+  _Optional plugin._
+
+* *echo.so*: RFC 862 plugin.  Start as inetd service, like time below.
+
+* *chargen.so*: RFC 864 plugin.  Start as inetd service, like time below.
+
+* *daytime.so*: RFC 867 plugin.  Start as inetd service, like time below.
+
+* *discard.so*: RFC 863 plugin.  Start as inetd service, like time below.
+
+* *rtc.so*: Restore and save system clock from/to RTC on boot/halt.
+
+* *initctl.so*: Extends finit with a traditional `initctl` functionality.
+
+* *modules-load.so*: Scans /etc/modules-load.d for modules to modprobe.
+
+* *netlink.so*: Listens to Linux kernel Netlink events for gateway and
+  interfaces.  These events are then sent to the Finit service monitor
+  for services that may want to be SIGHUP'ed on new default route or
+  interfaces going up/down.
+
+* *resolvconf.so*: Setup necessary files for `resolvconf` at startup.
+  _Optional plugin._
+
+* *time.so*: RFC 868 (rdate) plugin.  Start as inetd service.  Useful
+  for testing inetd filtering — BusyBox has an rdate (TCP) client.
+
+* *tty.so*: Watches `/dev`, using inotify, for new device nodes (TTY's)
+  to start/stop getty consoles on them on demand.  Useful when plugging
+  in a usb2serial converter to login to your embedded device.
+
+* *urandom.so*: Setup random seed at startup.
+
+* *x11-common.so*: Setup necessary files for X-Window.  _Optional plugin._
+
+Usually you want to hook into the boot process once, simple hook plugins
+like `bootmisc.so` are great for that purpose.  They are called at each
+hook point in the boot process, useful to insert some pre-bootstrap
+mechanisms, like generating configuration files, restoring HW device
+state, etc.  Available hook points are:
+
+
+Hooks
+-----
+
+### Bootstrap Hooks
+
+* `HOOK_ROOTFS_UP`: When `finit.conf` has been read and `/` has is
+  mounted — very early
+
+* `HOOK_BASEFS_UP`: All of `/etc/fstab` is mounted, swap is available
+  and default init signals are setup
+
+* `HOOK_NETWORK_UP`: System bootstrap, runlevel S, has completed and
+  networking is up (`lo` is up and the `network` script has run)
+
+* `HOOK_SVC_UP`: All services in the active runlevel has been launched
+
+* `HOOK_SYSTEM_UP`: All services *and* everything in `/etc/finit.d`
+  has been launched
+
+### Runtime Hooks
+
+* `HOOK_SVC_RECONF`: Called when the user has changed something in the
+  `/etc/finit.d` directory and issued `SIGHUP`.  The hook is called when
+  all modified/removed services have been stopped.  When the hook has
+  completed, Finit continues to start all modified and new services.
+
+* `HOOK_RUNLEVEL_CHANGE`: Called when the user has issued a runlevel
+  change.  The hook is called when services not matching the new
+  runlevel have been been stopped.  When the hook has completed, Finit
+  continues to start all services in the new runlevel.
+
+### Shutdown Hooks
+
+* `HOOK_SHUTDOWN`: Called at shutdown/reboot, right before all
+  services are sent `SIGTERM`
+
+Plugins like `initctl.so` and `tty.so` extend finit by acting on events,
+they are called I/O plugins and are called from the finit main loop when
+`poll()` detects an event.  See the source code for `plugins/*.c` for
+more help and ideas.