doc: add os services

Add a new 'OS Services' section to contain all dedicated os services
from other sections of the doc (reference and guides).

Signed-off-by: Anas Nashif <anas.nashif@intel.com>
diff --git a/doc/index-tex.rst b/doc/index-tex.rst
index 17578fd..4a9f6c3 100644
--- a/doc/index-tex.rst
+++ b/doc/index-tex.rst
@@ -19,6 +19,7 @@
    build/index.rst
    kernel/index.rst
    connectivity/index.rst
+   services/index.rst
    development_process/index.rst
    application/index.rst
    reference/index.rst
diff --git a/doc/index.rst b/doc/index.rst
index ba023bd..f1d8bf2 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -109,6 +109,7 @@
    build/index.rst
    kernel/index.rst
    connectivity/index.rst
+   services/index.rst
    reference/index.rst
    guides/index.rst
    security/index.rst
diff --git a/doc/services/index.rst b/doc/services/index.rst
new file mode 100644
index 0000000..d5e3bcf
--- /dev/null
+++ b/doc/services/index.rst
@@ -0,0 +1,8 @@
+.. _os_services:
+
+OS Services
+###########
+
+.. toctree::
+   :maxdepth: 1
+