The ESP32 Ethernet Kit has only a single GPIO pin exposed to SAUL via
`saul_gpio`, but that GPIO doubles as PHY clock input when `esp32_eth`
is used. Hence, the `saul_gpio` dep should be optional and only kick
in when `esp32_eth` is not used.
When using `make flash` or `make term` with `MOST_RECENT_PORT=1`, RIOT
should now select relatively robustly the most recently connected
ESP32 Ethernet Kit / ESP32 Wrover Kit board, even with other TTYs
present. This is because the FTDI Dual RS232-HS with two USB2UART
bridges in the chip would be an expensive overkill for most boards,
unless one is using the FTDI chip to big-bang JTAG as well - as done
on the Ethernet Kit and Wrover Kit boards.
- most were trivial
- missing group close or open
- extra space
- no doxygen comment
- name commad might open an implicit group
this hould also be implicit cosed but does not happen somtimes
- crazy: internal declared groups have to be closed internal
Fixes various issues in documentation:
- replaces HTML anchor tags in markdown headings by markdown heading IDs.
- replaces HTML linebreaks by newline commands
- replaces \htmlonly commands for image resizing by the width argument in \image commands
- uses more unique identifiers for references
- uses stable references for driver documentation
- fix broken links to external HTML documents
- replaces the TOC link in headers by a back to TOC link below each section
- replaces ``` fenced code blocks by ~~~
