Document more TF-M configurations

Add documentation for more TF-M-related configurations:
* TF-M version supported
* Support for TF-M bootloader and two image slots
* post binary hooks

Author: LDong-Arm

docs/porting/security/psa_targets_in_mbed-os.md

@@ -171,8 +171,14 @@ An Mbed OS (NSPE) target must contain the following attributes (in addition to o
 
 * `inherits`: PSA generic target `PSA_DUAL_CORE`, unless the target has to inherit
   from one of its family targets.
+* `extra_labels`: `TARGET_`[label] paths to enable.
+  * `TFM_LATEST`: If the latest release of TF-M is supported by the target.
+  * `TFM_V`[major]`_`[minor]: If a legacy release of TF-M supported.
+* `macros_add`: C/C++ macros that are globally set during compilation.
+  * `BL2`: If the TF-M bootloader is supported by the target.
+  * `MCUBOOT_IMAGE_NUMBER=2`: If the secure and non-secure images are in two separate bootloader slots.
 * `tfm_target_name`: Target name in TF-M.
-* `tfm_bootloader_supported`: If TF-M bootloader is supported by the target.
+* `tfm_bootloader_supported`: If the TF-M bootloader is supported by the target.
 
     The supported values are `true` and `false`.
 * `tfm_supported_toolchains`: Supported TF-M toolchains.
@@ -183,6 +189,11 @@ An Mbed OS (NSPE) target must contain the following attributes (in addition to o
     The supported values are `ARMCLANG` and `GNUARM`.
 * `tfm_delivery_dir`: The directory to which TF-M binaries will be copied.
 * `TFM_OUTPUT_EXT`: Optional attribute that indicates the output extension of the TF-M secure binary.
+* `post_binary_hook`:
+  * `function`: The target's post binary hook ([class].[method]) in `tools/targets/__init__.py` for image signing, required if the TF-M bootloader support is supported.
+* `secure_image_filename`: The file name of the TF-M secure binary, to be signed by the post binary hook.
+
+**Note**: When `inherits` is used, some of attributes are set by the PSA generic target.
 
 The following example shows a PSA enabled dual-core target, `PSoC64`:
 
@@ -272,8 +283,14 @@ and [porting targets](../porting/porting-the-hal-apis.html)):
 
 * `inherits`: PSA generic target `PSA_V8_M`, unless the target has to inherit from
   one of its family targets.
+* `extra_labels`: `TARGET_`[label] paths to enable.
+  * `TFM_LATEST`: If the latest release of TF-M is supported by the target.
+  * `TFM_V`[major]`_`[minor]: If a legacy release of TF-M supported.
+* `macros_add`: C/C++ macros that are globally set during compilation.
+  * `BL2`: If the TF-M bootloader is supported by the target.
+  * `MCUBOOT_IMAGE_NUMBER=2`: If the secure and non-secure images are in two separate bootloader slots.
 * `tfm_target_name`: Target name in TF-M.
-* `tfm_bootloader_supported`: If TF-M bootloader is supported by the target.
+* `tfm_bootloader_supported`: If the TF-M bootloader is supported by the target.
 
     The supported values are `true` and `false`.
 * `tfm_supported_toolchains`: Supported TF-M toolchains.
@@ -285,6 +302,11 @@ and [porting targets](../porting/porting-the-hal-apis.html)):
 
 * `tfm_delivery_dir`: The directory to which TF-M binary will be copied.
 * `TFM_OUTPUT_EXT`: Optional attribute that indicates the output extension of the TF-M secure binary.
+* `post_binary_hook`:
+  * `function`: The target's post binary hook ([class].[method]) in `tools/targets/__init__.py` for image signing, required if the TF-M bootloader support is supported.
+* `secure_image_filename`: The file name of the TF-M secure binary, to be signed by the post binary hook.
+
+**Note**: When `inherits` is used, some of attributes are set by the PSA generic target.
 
 The following example shows a PSA-enabled Armv8-M PSA target, `ARM_MUSCA_A1`: