README: Add information about ELL when building from sources

README

@@ -22,12 +22,42 @@ To compile and install run:
 	make && make install
 
 
+Embedded Linux library
+======================
+
+In order to compile the daemon and utilities the development version of
+Embedded Linux library is required to be present. The development
+repositories can be found here:
+
+	git://git.kernel.org/pub/scm/libs/ell/ell.git
+	https://kernel.googlesource.com/pub/scm/libs/ell/ell.git
+
+The build systems requires that the Embedded Linux library source code
+is available on the same top level directory as the source code:
+
+	.
+	|--- ell
+	|    |--- ell
+	|    `--- unit
+	`--- ofono
+	     |--- src
+	     `--- tools
+
+It is not required to build or install Embedded Linux library. The build
+will happen when building the Wireless daemon and it will then be linked
+internally.
+
+When using --enable-external-ell build option, it is not required that the
+Embedded Linux library source code is available in the top level directory.
+
+
 Kernel Dependencies
 ===================
 
 In order to have the PPP stack working in oFono you need to enable CONFIG_TUN
 (Universal TUN/TAP device driver support) in your kernel .config.
 
+
 Information
 ===========