Extend readme and describe how to setup the service

README.md

@@ -17,3 +17,29 @@ This is an openwrt feed that contains definitions to include CoreDNS software in
 3. install coredns packages into your build:
 
    `./scripts/feeds install -a -p feed_coredns`
+
+## service init
+
+The package setups an init script `/etc/init.d/coredns` and uci config section:
+
+```
+config coredns 'main'
+	option port '53'
+	option config '/etc/coredns/Corefile'
+```
+
+There are two options defined:
+- port, default: 53 -- a port where coredns will listen for connections
+- config, default: /etc/coredns/Corefile -- a Corefile config file
+
+> Use `uci` tool to change these values, e.g.: `uci set coredns.main.port=1053'
+
+## coredns configuration
+
+The package provides an empty config `Corefile` located at `/etc/coredns/Corefile`.
+The empty `Corefile`:
+
+```
+. { }
+```
+