doc: add Bluetooth LE Controller documentation

Add a user guide that describes what Bluetooth LE Controllers
are available and what they support.

Signed-off-by: Ruth Fuchss <[email protected]>

Author: Ruth Fuchss

doc/nrf/ug_ble_controller.rst

@@ -0,0 +1,58 @@
+.. _ug_ble_controller:
+
+Bluetooth LE Controller
+#######################
+
+When you develop a Bluetooth Low Energy (LE) application, you must include a Bluetooth LE Controller.
+A Bluetooth LE Controller is the layer of the Bluetooth stack that handles the physical layer packets and all associated timing.
+It implements the Link Layer, which is the low-level, real-time protocol that controls the Bluetooth LE communication.
+
+The |NCS| contains two implementations of a Bluetooth LE Controller:
+
+* `nRF Bluetooth LE Controller`_
+* `Zephyr Bluetooth LE Controller`_
+
+The nRF Bluetooth LE Controller is implemented by Nordic Semiconductor.
+The Zephyr Bluetooth LE Controller is an open source Link Layer developed in the `Zephyr Project`_, to which Nordic Semiconductor is a contributor.
+
+Both Link Layers integrate with the Zephyr Bluetooth LE Host, which completes the full Bluetooth LE protocol stack solution in the |NCS|.
+It is possible to select either Bluetooth LE Controller for application development.
+See `Usage in samples`_ for more information.
+
+
+nRF Bluetooth LE Controller
+***************************
+
+The :ref:`nRF Bluetooth LE Controller <nrfxlib:ble_controller>` is designed for nRF52 and nRF53 Series devices.
+It provides the same implementation of the Link Layer that is available as part of Nordic Semiconductor's SoftDevices.
+The nRF Bluetooth LE Controller is developed, tested, and supported by Nordic Semiconductor.
+
+The nRF Bluetooth LE Controller is distributed as a set of precompiled, linkable libraries that can be found in the `nrfxlib`_ repository.
+There are different variants of the libraries that support different feature sets.
+Which variant you should choose depends on the chip that you are using, the features that you need, and the amount of available memory.
+
+Nordic's Bluetooth LE Controller supports an extensive standard feature set from the Bluetooth 5.2 specification and a number of extensions for high-performance applications like Low Latency Packet mode (LLPM).
+See the :ref:`nRF Bluetooth LE Controller documentation <nrfxlib:ble_controller>` for a detailed list of supported features.
+
+
+Zephyr Bluetooth LE Controller
+******************************
+
+The `Zephyr Project`_ has a full, open source, :ref:`Bluetooth Low Energy stack <zephyr:bluetooth-arch>`, which includes the Zephyr Bluetooth LE Controller.
+This Bluetooth LE Controller is designed with an upper and lower implementation to make it possible to support multiple hardware platforms.
+It is developed by the Zephyr community and provided as open source.
+
+To use Zephyr's Bluetooth LE Controller in your application, include a :ref:`Controller-only build <zephyr:bluetooth-build-types>` of the Bluetooth LE stack.
+
+Zephyr's Bluetooth LE Controller supports most of the standard Bluetooth LE features, except for Advertising Extensions.
+See the :ref:`Zephyr documentation <zephyr:bluetooth-overview>` for a detailed list of supported features.
+
+
+Usage in samples
+****************
+
+Most :ref:`Bluetooth LE samples <ble_samples>` in the |NCS| can use either Bluetooth LE Controller.
+An exception is the :ref:`ble_llpm` sample, which requires the nRF Bluetooth LE Controller that supports LLPM.
+
+By default, all samples except for the :ref:`ble_llpm` sample are currently configured to use Zephyr's Bluetooth LE Controller.
+To use the nRF Bluetooth LE Controller instead, set :option:`CONFIG_BT_LL_NRFXLIB_DEFAULT` to ``y`` in the :file:`prj.conf` file (see :ref:`configure_application`) and make sure to build from a clean build directory.

doc/nrf/ug_bt_ll_nrfxlib.rst

@@ -14,7 +14,7 @@ They introduce you to important concepts and guide you through developing your a
    ug_nrf9160
    ug_nrf5340
    ug_thingy91
-   ug_bt_ll_nrfxlib
+   ug_ble_controller
    ug_esb
    ug_multi_image
    ug_bootloader

doc/nrf/user_guides.rst

@@ -244,7 +244,7 @@ Documentation
 
 * Added or updated the following documentation:
 
-  * :ref:`ug_bt_ll_nrfxlib`
+  * nRF BLE Controller (experimental)
   * :ref:`ug_multi_image`
   * :ref:`partition_manager`
   * :ref:`nrf_desktop`