DOC: Document IPUWorkflow and phases

TODO: the file is missing

Author: pirat89

docs/source/upgrade-architecture-and-workflow/index.rst

@@ -7,7 +7,9 @@ TBD
     :caption: Contents:
     :glob:
 
+    phases-overview
     dracut-modules-and-upgrade-initramfs
+    target-userspace-creator
 
 
 .. Indices and tables