Update service deployment documentation

Updates the old portability model page to better describe how
service provider deployments for different environments and
platforms are organised. Introduces a more flexible directory
structure that improves reuse and extensibility for service
provider deployments.

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I5635c38210cbb55d993150e8efe9e84b95acdf49
diff --git a/docs/deployments/index.rst b/docs/deployments/index.rst
index 40a6949..bc98e61 100644
--- a/docs/deployments/index.rst
+++ b/docs/deployments/index.rst
@@ -17,10 +17,10 @@
     libraries
     tools-demo-apps
 
-Related deployments:
+Related documentsments:
 
   - :ref:`Project Structure`
-  - :ref:`Portability Model`
+  - :ref:`Service Deployment Model`
   - :ref:`Build Instructions`
   - :ref:`Running Tests`