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/contributing/maintainers.rst b/docs/contributing/maintainers.rst
index 546c42f..a8bf34c 100644
--- a/docs/contributing/maintainers.rst
+++ b/docs/contributing/maintainers.rst
@@ -123,6 +123,22 @@
     :github: `RaymondNgun <https://github.com/RaymondNgun>`__
 
 
+Nordic Semiconductor Platforms
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Ioannis Glaropoulos
+    :email: `ioannis.glaropoulos@nordicsemi.no <ioannis.glaropoulos@nordicsemi.no>`__
+    :github: `ioannisg <https://github.com/ioannisg>`__
+
+Andrzej Głąbek
+    :email: `andrzej.glabek@nordicsemi.no <andrzej.glabek@nordicsemi.no>`__
+    :github: `anangl <https://github.com/anangl>`__
+
+Øyvind Rønningstad
+    :email: `oyvind.ronningstad@nordicsemi.no <oyvind.ronningstad@nordicsemi.no>`__
+    :github: `oyvindronningstad <https://github.com/oyvindronningstad>`__
+
+
 =============
 
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