Troubleshooting: Add more recent FAQs

Signed-off-by: Stefan Wahren <stefan.wahren@chargebyte.com>

Author: lategoodbye

docs/source/troubleshooting.rst

@@ -41,6 +41,14 @@ and a `library <https://github.com/EVerest/everest-core/tree/main/lib/everest/ca
 which uses the CAN interface. This might help as a starting point.
 
 
+How can I access the GPIOs under Linux?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Since the GPIO sysfs interface /sys/class/gpio has been deprecated since Linux 4.8,
+we recommend the usage of chardev GPIO and libgpiod. The modification of the bias
+settings via libgpiod is not yet implemented, so it needs to be done via device tree.
+
+
 What is the difference between CHSTOP_IN and SAFETY_ESTOPx?
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
@@ -50,6 +58,50 @@ for timing critical use cases. Currently there is no EVerest module, which is ab
 In order to realize realtime emergency stop behavior use the SAFETY_ESTOPx signals, which are connected to the safety processor.
 
 
+How can I list the available UARTs?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+All UARTs of the i.MX93 are handled by the fsl-lpuart driver, so the following
+command should list all available UARTs. Please keep in mind that Linux starts
+counting from zero (ttyLP0 = UART1, ...).
+
+.. code-block::
+
+   root@chargesom:/# cat /proc/tty/driver/fsl-lpuart
+   serinfo:1.0 driver revision:
+   0: uart:FSL_LPUART mmio:0x44380010 irq:17 tx:9932 rx:0 RTS|CTS|DTR|DSR|CD
+   2: uart:FSL_LPUART mmio:0x42570010 irq:18 tx:12966 rx:26572 RTS|CTS|DTR|DSR|CD
+   3: uart:FSL_LPUART mmio:0x42580010 irq:19 tx:936 rx:617 RTS|CTS|DTR|DSR|CD
+   4: uart:FSL_LPUART mmio:0x42590010 irq:20 tx:0 rx:0 CTS|DSR|CD
+
+
+How can I print the current pin/pad control settings (e.g. bias, drive strength)?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The current PAD control settings are available under Linux only via debugfs,
+but this requires an equivalent pinctrl setting within the device tree:
+
+.. code-block::
+
+   cat /sys/kernel/debug/pinctrl/443c0000.pinctrl/pinconf-pins
+   Pin config settings per pin
+   Format: pin (name): configs
+   pin 0 (IMX93_IOMUXC_DAP_TDI): . .
+
+
+Which LVDS displays have been tested with the Charge SOM EVB?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The `Distec DD-0700-MC01 <https://www.fortec-integrated.de/en/products/tft-components/tft-displays/detail/fortec-integrated/dd-0700-mc01/>`_
+(7 inch, 800x480 resolution) has been tested with the Charge SOM EVB.
+
+
+I like to create my own DT overlay. Is there an example?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Yes, please have a look at this `commit <https://github.com/chargebyte/linux/commit/125a587a0cf7e8d9db1fdddf9383a67c2b46d107>`_ .
+
+
 Where can I find the device tree sources of the Charge SOM?
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^