docs: add "Supported targets" page

docs/faq.rst

@@ -141,6 +141,8 @@ At the same time, Rust has other advantages:
     Go can.
 
 
+.. _faq-esp:
+
 What about the ESP8266/ESP32?
 -----------------------------
 

docs/index.rst

@@ -12,6 +12,7 @@ Contents:
    :maxdepth: 2
 
    installation
+   targets
    microcontrollers
    faq
    internals

docs/targets.rst

@@ -0,0 +1,32 @@
+.. targets:
+
+.. |br| raw:: html
+
+    <br>
+
+Supported targets
+=================
+
+The following boards are currently supported:
+
+  * `Arduino Uno <https://store.arduino.cc/arduino-uno-rev3>`_ (`ATmega328p
+    <https://www.microchip.com/wwwproducts/en/ATmega328p>`_) |br|
+    Note: the AVR backend of LLVM is still experimental so you may encounter
+    bugs.
+  * `BBC micro:bit <https://microbit.org/>`_ (`nRF51822
+    <https://www.nordicsemi.com/eng/Products/Bluetooth-low-energy/nRF51822>`_)
+  * `Nordic PCA10040
+    <https://www.nordicsemi.com/eng/Products/Bluetooth-low-energy/nRF52-DK>`_
+    (`nRF52832
+    <https://www.nordicsemi.com/eng/Products/Bluetooth-low-energy/nRF52832>`_)
+  * `nRF52840-MDK <https://wiki.makerdiary.com/nrf52840-mdk/>`_ (`nRF52840
+    <https://www.nordicsemi.com/eng/Products/nRF52840>`_)
+  * `QEMU <https://wiki.qemu.org/Documentation/Platforms/ARM>`_ (`LM3S6965
+    <http://www.ti.com/product/LM3S6965>`_) |br|
+    This target is supported only for testing purposes. It has not been tested
+    on real hardware.
+
+
+.. note::
+   Support for the ESP8266/ESP32 chips will take a lot of work if they ever get
+   support. See :ref:`this FAQ entry <faq-esp>` for details.