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/tfm_user_guide.rst b/docs/getting_started/tfm_user_guide.rst
index 55648f4..d2b0193 100644
--- a/docs/getting_started/tfm_user_guide.rst
+++ b/docs/getting_started/tfm_user_guide.rst
@@ -5,8 +5,8 @@
 SSE-200 subsystem on the MPS2 board and on the Fast Model(FVP).
 
 Follow :doc:`build instruction <tfm_build_instruction>` to build the binaries.
-Follow :doc:`secure boot <tfm_secure_boot>` to build the binaries with or
-without BL2 bootloader.
+Follow :doc:`secure boot </docs/technical_references/tfm_secure_boot>` to build the
+binaries with or without BL2 bootloader.
 
 ****************************************************************
 Execute TF-M example and regression tests on MPS2 boards and FVP
@@ -565,7 +565,7 @@
 Firmware upgrade and image validation with BL2 bootloader
 =========================================================
 High level operation of BL2 bootloader and instructions for testing firmware
-upgrade is described in :doc:`secure boot <tfm_secure_boot>`.
+upgrade is described in :doc:`secure boot </docs/technical_references/tfm_secure_boot>`.
 
 --------------
 
@@ -576,4 +576,4 @@
 .. _Keil MDK: http://www2.keil.com/mdk5
 .. _Keil MDK Documentation: https://www2.keil.com/mdk5/docs
 
-*Copyright (c) 2017-2020, Arm Limited. All rights reserved.*
+*Copyright (c) 2017-2021, Arm Limited. All rights reserved.*