[PATCH v7 0/3] tty: Introduce software RS485 direction control support

[Matwey V. Kornilov]

Changes from v6:
 - minor style changes
 - timers are not IRQSAFE now
Changes from v5:
 - rs485_emul variable has been renamed to em485 to follow function names convention
Changes from v4:
 - Add commit message to 1/3
Changes from v3:
 - Completely redesigned.
Changes from v2:
 - Introduced SER_RS485_SOFTWARE to show that software implementation is being used
 - serial8250_rs485_config is located as required
 - Timers are used to implement delay_before and delay_after timeouts

Signed-off-by: Matwey V. Kornilov <matwey@xxxxxxxxxx>