Documentation: networking: document ISO 15765-2

Document basic concepts, APIs and behaviour of the ISO 15675-2 (ISO-TP)
CAN stack.

Signed-off-by: Francesco Valla <valla.francesco@gmail.com>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Link: https://lore.kernel.org/all/20240501092413.414700-2-valla.francesco@gmail.com


Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>