Docs: Add MCUboot to the external dependencies

Add the MCUboot project to the list of external dependencies and
the command how to clone its required version.

Change-Id: Ic2e380c72fa7d5b12edec3a17ab20f6aaa407618
Signed-off-by: David Vincze <david.vincze@linaro.org>
diff --git a/docs/getting_started/tfm_build_instruction.rst b/docs/getting_started/tfm_build_instruction.rst
index fd80b03..8a0198a 100644
--- a/docs/getting_started/tfm_build_instruction.rst
+++ b/docs/getting_started/tfm_build_instruction.rst
@@ -30,6 +30,7 @@
     git clone https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git
     git clone https://github.com/ARMmbed/mbed-crypto.git -b mbedcrypto-3.0.1
     git clone https://git.trustedfirmware.org/TF-M/tf-m-tests.git
+    git clone https://github.com/JuulLabs-OSS/mcuboot.git -b v1.6.0
 
 .. Note::
    For building with Armclang compiler version 6.10.0, please follow the note
diff --git a/docs/getting_started/tfm_sw_requirement.rst b/docs/getting_started/tfm_sw_requirement.rst
index 2c52c3c..a2518d8 100644
--- a/docs/getting_started/tfm_sw_requirement.rst
+++ b/docs/getting_started/tfm_sw_requirement.rst
@@ -128,6 +128,8 @@
 
     - `Mbed Crypto library <https://github.com/ARMmbed/mbed-crypto>`__ v3.0.1
       is used as crypto library on the secure side
+    - `MCUboot <https://github.com/JuulLabs-OSS/mcuboot>`__ v1.6.0 is used as
+      the default bootloader in TF-M
 
 And the following TF-M projects as well:
     - `TF-M tests <https://git.trustedfirmware.org/TF-M/tf-m-tests.git>`__
@@ -139,6 +141,7 @@
 
     .
     ├── mbed-crypto
+    ├── mcuboot
     ├── tf-m-tests
     └── trusted-firmware-m
 
@@ -482,6 +485,7 @@
    "GNU Make",See `Supported GNU make versions`_,
    "tf-m-tests",See `External dependencies`_,
    "mbed-crypto",See `External dependencies`_,
+   "MCUboot",See `External dependencies`_,
    "Python",3.x,"Firmware, User Guide"
    "yaml",,"Firmware"
    "pyasn1",,"Firmware"