fconf: Add namespace guidance inside documentation

Change-Id: I50707d1836c7f5e4ef162c00256624a1f278baef
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>

docs/components/fconf.rst

@@ -83,3 +83,30 @@ This function will call all the ``populate()`` callbacks which have been
 registered with ``FCONF_REGISTER_POPULATOR()``.
 
 .. uml:: ../resources/diagrams/plantuml/fconf_bl2_populate.puml
+
+Namespace guidance
+~~~~~~~~~~~~~~~~~~
+
+As mentioned above, properties are logically grouped around namespaces and
+sub-namespaces. The following concepts should be considered when adding new
+properties/namespaces.
+The framework differentiates two types of properties:
+ - Properties used inside common code.
+ - Properties used inside platform specific code.
+
+The first category applies to properties being part of the firmware and shared
+across multiple platforms. They should be globally accessible and defined
+inside the ``lib/fconf`` directory. The namespace must be chosen to reflect the
+feature/data abstracted.
+Example:
+ - |TBBR| related properties: tbbr.cot.bl2_id
+ - Dynamic configuration information: dyn_cfg.dtb_info.hw_config_id
+
+The second category should represent the majority of the properties defined
+within the framework: Platform specific properties. They must be accessed only
+within the platform API and are defined only inside the platform scope. The
+namespace must contain the platform name under which the properties defined
+belong.
+Example:
+ - Arm io framework: arm.io_policies.bl31_id
+