doc: releases: rework linkage to old release notes/migration guides

Move the link to old release notes and migration guides to the bottom of
the document

Signed-off-by: Benjamin Cabé <benjamin@zephyrproject.org>

doc/releases/eol_releases.rst

@@ -1,7 +1,15 @@
-End-of-life releases
+.. _eol_releases:
-====================
 
-Release notes for end-of-life releases of Zephyr RTOS are kept here for historical purposes.
+End-of-life releases
+####################
+
+Release notes and migration guides for end-of-life releases of Zephyr RTOS are kept here for
+historical purposes.
+
+.. _eol_releases_relesase_notes:
+
+Release Notes
+*************
 
 .. toctree::
    :maxdepth: 1
@@ -12,3 +20,15 @@ Release notes for end-of-life releases of Zephyr RTOS are kept here for historic
    release-notes-1.*
    release-notes-2.[0-6]
    release-notes-3.[0-5]
+
+.. _eol_releases_migration_guides:
+
+Migration Guides
+****************
+
+.. toctree::
+   :maxdepth: 1
+   :glob:
+   :reversed:
+
+   migration-guide-3.[5]

doc/releases/index.rst

@@ -81,7 +81,6 @@ needs to be changed are to be detailed in the release's migration guide.
    :glob:
    :reversed:
 
-   eol_releases
    release-notes-2.7
    release-notes-3.[6-7]
    release-notes-4.0
@@ -115,7 +114,20 @@ to be able to understand the context of the change.
    :glob:
    :reversed:
 
-   migration-guide-*
+   migration-guide-3.[6-7]
+   migration-guide-4.[0]
+
+End-of-life Releases
+********************
+
+.. toctree::
+   :hidden:
+   :maxdepth: 1
+
+   eol_releases
+
+Release notes and migration guides for end-of-life releases of Zephyr RTOS can be accessed
+:ref:`here <eol_releases>`.
 
 .. _`GitHub repository`: https://github.com/zephyrproject-rtos/zephyr
 .. _`GitHub tagged releases`: https://github.com/zephyrproject-rtos/zephyr/tags