Merge branch 'references' into 'master'

Add more links to data sheets in the hardware section.

See merge request Librem5/developer.puri.sm!125

Hardware_Reference.rst

@@ -13,8 +13,11 @@ developer kits contained in `this blog post <https://puri.sm/posts/librem5-2018-
 Librem 5 Devkit
 ---------------
 
-  * Customer grade i.MX 8M Quad CPU (4 cores)
+  * `Customer grade i.MX 8M Quad <https://www.nxp.com/products/processors-and-microcontrollers/arm-based-processors-and-mcus/i.mx-applications-processors/i.mx-8-processors/i.mx-8m-family-armcortex-a53-cortex-m4-audio-voice-video:i.MX8M>`_ [`datasheet <https://www.nxp.com/docs/en/data-sheet/IMX8MDQLQIEC.pdf>`_]
+    and [`reference manual <https://www.nxp.com/webapp/Download?colCode=IMX8MDQLQRM>`_]
 
+    * Four ARM Cortex A54 cores.
+    * One Cortex M4.
     * Vivante GC7000Lite graphics
     * 1 x Gigabit Ethernet
 
@@ -29,7 +32,8 @@ Librem 5 Devkit
   * HDMI output via Mini-HDMI
   * Rocktech JH057N00900 MIPI DSI LCD panel: 720x1440 pixels and touch
     controller
-  * MIPI CSI Camera
+  * Omnivision OV5642 MIPI CSI Camera `[datasheet <https://cdn.sparkfun.com/datasheets/
+    Sensors/LightImaging/OV5640_datasheet.pdf>`_]
   * Hardware kill switches for
 
     * WWAN (Modem)
@@ -42,7 +46,7 @@ Librem 5 Devkit
   * Headphones and external microphone via CTIA-configured 3.5mm jack
   * Bluetooth I2S interface
   * Bluetooth (UART4)
-  * ublox MAX-M8Q GNSS (UART interface and antenna)
+  * ublox MAX-M8Q GNSS (UART3 interface and antenna)
   * Haptic motor
   * ST LSM9D1 accelerometer, gyro, magnetometer
   * JTAG header (unpopulated)