openthread: kconfig: rework OpenThread security configurations

With the updates to mbedTLS Kconfig it is now possible to update the
OpenThread security configurations by disabling the mbedTLS prompt and
avoid stuck symbol selection.

As part of this, the OpenThread security selection has been reworked
into a choice which ensures only a single security selection can be
chosen.

And the OPENTHREAD_MBEDTLS itself has been made promptless to ensure
other parts of the build system can select a specific OpenThread
security implementation and disable user selection, if the module or
sample require such behavior.

Signed-off-by: Torsten Rasmussen <[email protected]>
Signed-off-by: Ioannis Glaropoulos <[email protected]>

Author: tejlmand

subsys/net/l2/openthread/Kconfig

@@ -2,6 +2,12 @@
 
 # Copyright (c) 2018 Nordic Semiconductor ASA
 # SPDX-License-Identifier: Apache-2.0
+config OPENTHREAD_SECURITY_INTERNAL
+	bool
+	help
+	  OpenThread setting to signal that OpenThread security settings, such
+	  as the OPENTHREAD_MBEDTLS setting will be controlled through other
+	  Kconfig dependencies and should not be user configurable.
 
 menuconfig NET_L2_OPENTHREAD
 	bool "OpenThread L2"
@@ -153,9 +159,32 @@ config OPENTHREAD_SHELL
 	depends on SHELL
 	default y
 
+config MBEDTLS_PROMPTLESS
+	bool
+	default y if !CUSTOM_OPENTHREAD_SECURITY
+
+choice OPENTHREAD_SECURITY
+	prompt "OpenThread security"
+	default OPENTHREAD_MBEDTLS_CHOICE
+	depends on !OPENTHREAD_SECURITY_INTERNAL
+
+config CUSTOM_OPENTHREAD_SECURITY
+	bool "Custom"
+	help
+	  Security settings will be controlled directly by the user.
+	  Enabling this setting will give access to full control of mbed TLS
+	  configuration.
+
+config OPENTHREAD_MBEDTLS_CHOICE
+	bool "mbed TLS built-in"
+	select OPENTHREAD_MBEDTLS
+	help
+	  Use the OpenThread mbed TLS configuration pre-defined security scheme.
+
+endchoice
+
 config OPENTHREAD_MBEDTLS
-	bool "Enable built-in mbedtls for use with OpenThread"
-	default y
+	bool
 	select MBEDTLS
 	select MBEDTLS_ENABLE_HEAP
 	select MBEDTLS_CIPHER_AES_ENABLED