doc: remove warning "file not included in toctree"

Files that are included directly into other files are not referenced
in TOC trees. Quiet warning by tagging them :orphan:

Change-Id: I3a975420ce366ca155e8c0158dcd0fb7c094a4a0
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
diff --git a/doc/README.rst b/doc/README.rst
index 1a20b2a..c7ff3ba 100644
--- a/doc/README.rst
+++ b/doc/README.rst
@@ -1,3 +1,5 @@
+:orphan:
+
 Welcome to Zephyr Kernel
 ########################
 
@@ -71,4 +73,4 @@
 If you want the LaTeX PDF output, you need to install all the Latex
 packages first. That installation is beyond the scope of this document.
 
-.. _ReST documentation: http://sphinx-doc.org/rest.html
\ No newline at end of file
+.. _ReST documentation: http://sphinx-doc.org/rest.html
diff --git a/doc/about_zephyr.rst b/doc/about_zephyr.rst
index b2c7399..cecf198 100644
--- a/doc/about_zephyr.rst
+++ b/doc/about_zephyr.rst
@@ -1,3 +1,5 @@
+:orphan:
+
 .. _about_zephyr:
 
 Introduction to the Zephyr Project
diff --git a/doc/contribute/coding_style.rst b/doc/contribute/coding_style.rst
index 4c5556c..e88bef8 100644
--- a/doc/contribute/coding_style.rst
+++ b/doc/contribute/coding_style.rst
@@ -1,3 +1,5 @@
+:orphan:
+
 .. _coding_style:
 
 Coding Style
diff --git a/doc/contribute/error_code_conventions.rst b/doc/contribute/error_code_conventions.rst
index 28d4ad7..2164027 100644
--- a/doc/contribute/error_code_conventions.rst
+++ b/doc/contribute/error_code_conventions.rst
@@ -1,3 +1,5 @@
+:orphan:
+
 .. _error_code_conventions:
 
 Return Codes
diff --git a/doc/contribute/maintainers.rst b/doc/contribute/maintainers.rst
index 6add117..7ac2db6 100644
--- a/doc/contribute/maintainers.rst
+++ b/doc/contribute/maintainers.rst
@@ -1,3 +1,5 @@
+:orphan:
+
 .. _maintainers:
 
 Information Regarding Maintainers
@@ -8,4 +10,4 @@
 Once a change is sent to Gerrit for review the maintainers
 receive an email requesting them to review the change. The master
 branch should never be rebased. Code can be reverted as necessary,
-instead of rewriting the history.
\ No newline at end of file
+instead of rewriting the history.
diff --git a/doc/crypto/crypto.rst b/doc/crypto/crypto.rst
index 77d7738..8079b95 100644
--- a/doc/crypto/crypto.rst
+++ b/doc/crypto/crypto.rst
@@ -1,3 +1,5 @@
+:orphan:
+
 Cryptography
 ############
 
diff --git a/doc/drivers/synchronous_call.rst b/doc/drivers/synchronous_call.rst
index cb85188..f93edcb 100644
--- a/doc/drivers/synchronous_call.rst
+++ b/doc/drivers/synchronous_call.rst
@@ -1,3 +1,5 @@
+:orphan:
+
 .. _synchronous_call:
 
 Synchronous Calls
diff --git a/doc/substitutions.rst b/doc/substitutions.rst
index 186ed95..bb154a5 100644
--- a/doc/substitutions.rst
+++ b/doc/substitutions.rst
@@ -1,3 +1,5 @@
+:orphan:
+
 .. |codename| replace:: Zephyr Kernel
 
 .. |project| replace:: Zephyr Project