docs: Documentation restructure

- Change main index structure
- Sort out integration and porting guidelines
- Resort table with releases
- Add Tools section. To be adjusted further for tf-m-tools

Intention to minimise files movement to simplify review process.
Affected files shall be moved later after the new structure agreement.

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: I0352bebabe09d4f7b5e8848ee620c0cea6881c94
diff --git a/docs/contributing/doc_guidelines.rst b/docs/contributing/doc_guidelines.rst
index d5c5967..dcc9732 100644
--- a/docs/contributing/doc_guidelines.rst
+++ b/docs/contributing/doc_guidelines.rst
@@ -20,7 +20,7 @@
 
 - If the patch modifies a present file, the file's style should be followed
 - If creating a new file,
-  :doc:`integration guide </integration_guide/tfm_integration_guide>` can be used as a reference.
+  :doc:`integration guide </integration_guide/index>` can be used as a reference.
 - When a new style is to be expressed, consult the `Python Documentation Guidelines`_
 
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