Docs: Restructure the documents

Restructure the file category to let it more friendly to users.

Signed-off-by: Summer Qin <summer.qin@arm.com>
Change-Id: I7ced0e2d700ce03423e472e0098608f3445ba169
diff --git a/docs/getting_started/index.rst b/docs/getting_started/index.rst
index 4b08906..c6d8d34 100644
--- a/docs/getting_started/index.rst
+++ b/docs/getting_started/index.rst
@@ -2,12 +2,15 @@
 ======================
 .. toctree::
     :maxdepth: 1
-    :caption: Contents
     :glob:
     :numbered:
 
-    *
+    tfm_sw_requirement
+    tfm_build_instruction
+    tfm_build_instruction_iar
+    tfm_user_guide
+    /tools/index
 
 --------------
 
-*Copyright (c) 2020, Arm Limited. All rights reserved.*
+*Copyright (c) 2020-2021, Arm Limited. All rights reserved.*