Update README with latest docs modifications

Change-Id: If00a115e7f58ed6f2fcd6d4ebe00d96df58c0747
Signed-off-by: Romain Forlot <romain.forlot@iot.bzh>

1 files changed, 36 insertions, 2 deletions

diff --git a/README.md b/README.md
index 64f3379..218ce30 100644
--- a/README.md
+++ b/README.md
@@ -283,7 +283,12 @@ SET_TARGET_PROPERTIES(${TARGET_NAME} PROPERTIES
 > targets. This is already handle by template and will be installed in the
 > following path : **${CMAKE_INSTALL_PREFIX}/${PROJECT_NAME}**
 
-#### Add external 3rd party library
+> **NOTE**: if you want to set and use `rpath` with your target you should use
+> and set the target property `INSTALL_RPATH`.
+
+## Add external 3rd party library
+
+### Build, link and ship external library with the project
 
 You could need to include an external library that isn't shipped in the
 platform. Then you have to bundle the required library in the `lib` widget
@@ -329,9 +334,13 @@ add_dependencies(${TARGET_NAME} ${MXML})
 
 Here we define an external project that drive the build of the library then we
 define new CMake target of type **IMPORTED**. Meaning that this target hasn't
-be built using CMake but is available at the location defined in the target
+been built using CMake but is available at the location defined in the target
 property *IMPORTED_LOCATION*.
 
+You could want to build the library as *SHARED* or *STATIC* depending on your needs
+and goals. Then you only have to modify the external project configure step and change
+filename used by **IMPORTED** library target defined after external project.
+
 Then target *LABELS* property is set to **LIBRARY** to ship it in the widget.
 
 Unicens project also need some header from this library, so we use the target
@@ -340,6 +349,31 @@ to that imported target, it can access to the include directories.
 
 We bound the target to the external project using a CMake dependency at last.
 
+Then this target could be use like any other CMake target and be linked etc.
+
+### Only link and ship external library with the project
+
+If you already have a binary version of the library that you want to use and you
+can't or don't want to build the library then you only have to add an **IMPORTED**
+library target.
+
+So, taking the above example, `mxml` library inclusion would be:
+
+```cmake
+PROJECT_TARGET_ADD(mxml)
+
+add_library(${TARGET_NAME} SHARED IMPORTED GLOBAL)
+
+SET_TARGET_PROPERTIES(${TARGET_NAME} PROPERTIES
+    LABELS LIBRARY
+    IMPORTED_LOCATION /path/to/library/libmxml.so.1
+    INTERFACE_INCLUDE_DIRECTORIES /path/to/mxml/include/dir
+)
+```
+
+Finally, you can link any other lib or executable target with this imported
+library like any other target.
+
 #### Macro reference
 
 ##### PROJECT_TARGET_ADD