Platform: Add support for new SOCs: nRF5340 and nRF9160

Supporting most configurations.

This patch targets the nRF9160 and the nRF5340 application core.

The nRF5340 is a dual-core SOC (application core and network core). The
nRF5340 application core is a Cortex-M33F with TrustZone-M.

The nRF9160 is an SOC with LTE-M/NB-IOT/GPS connectivity. The nRF9160 has
a Cortex-M33F with TrustZone-M.

Common code between the two platforms has been placed into a common
directory.

The platforms do not use the tfm_common_s.ld linker script since the nRF
IDAU needs some alterations to the placement of the veneers.

The common directory contains parts of the nrfx driver framework,
copied from https://github.com/NordicSemiconductor/nrfx version 2.3.0
at commit 6c31cb7d0e4038afa1efc9bfed40206adfd7b83e.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>
Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
Signed-off-by: Øyvind Rønningstad <oyvind.ronningstad@nordicsemi.no>
Change-Id: I15b932f444aa9adf2ef2489e9ecf036c64c851a7
diff --git a/docs/introduction/readme.rst b/docs/introduction/readme.rst
index 55fdd5b..e8fb4e7 100644
--- a/docs/introduction/readme.rst
+++ b/docs/introduction/readme.rst
@@ -141,6 +141,10 @@
           <https://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-mpu-eval-tools/stm32-mcu-mpu-eval-tools/stm32-nucleo-boards/nucleo-l552ze-q.html>`_
         - `DISCO L562QE.
           <https://www.st.com/content/st_com/en/products/evaluation-tools/product-evaluation-tools/mcu-mpu-eval-tools/stm32-mcu-mpu-eval-tools/stm32-discovery-kits/stm32l562e-dk.html>`_
+        - `nRF9160 DK (nordic_nrf/nrf9160dk_nrf9160).
+          <https://www.nordicsemi.com/Software-and-tools/Development-Kits/nRF9160-DK>`_
+        - `nRF5340 PDK (nordic_nrf/nrf5340pdk_nrf5340_cpuapp).
+          <https://www.nordicsemi.com/Software-and-tools/Development-Kits/nRF5340-PDK>`_
 
     - Cortex-M23 system: