trezord: add docs

nixos/modules/services/hardware/trezord.nix

@@ -4,6 +4,12 @@ with lib;
 let
   cfg = config.services.trezord;
 in {
+
+  ### docs
+
+  meta = {
+    doc = ./trezord.xml;
+  };
   
   ### interface
 

nixos/modules/services/hardware/trezord.xml

@@ -0,0 +1,26 @@
+<chapter xmlns="http://docbook.org/ns/docbook"
+         xmlns:xlink="http://www.w3.org/1999/xlink"
+         xmlns:xi="http://www.w3.org/2001/XInclude"
+         version="5.0"
+         xml:id="trezor">
+ <title>Trezor</title>
+ <para>
+  Trezor is an open-source cryptocurrency hardware wallet and security token
+  allowing secure storage of private keys.
+ </para>
+ <para>
+  It offers advanced features such U2F two-factor authorization, SSH login
+  through
+  <link xlink:href="https://wiki.trezor.io/Apps:SSH_agent">Trezor SSH agent</link>,
+  <link xlink:href="https://wiki.trezor.io/GPG">GPG</link> and a
+  <link xlink:href="https://wiki.trezor.io/Trezor_Password_Manager">password manager</link>.
+  For more information, guides and documentation, see <link xlink:href="https://wiki.trezor.io"/>.
+ </para>
+ <para>
+  To enable Trezor support, add the following to your <filename>configuration.nix</filename>:
+<programlisting>
+<xref linkend="opt-services.trezord.enable"/> = true;
+</programlisting>
+  This will add all necessary udev rules and start Trezor Bridge.
+ </para>
+</chapter>