This adds support for delays between assertion of RTS (which is supposed to enable the rs485 transmitter) and sending as well as between the last send char and deassertionof RTS. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Link: https://lore.kernel.org/r/20200714093012.21621-2-uwe@kleine-koenig.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>