Marks DTC as supported in the peripheral table (normal mode only, used
by SCI) and documents the SCI driver features: the per-instance
FIFO/DTC mutual exclusion and the measured overrun-margin trade-off
between them, termios TCGETS/TCSETS support (tested up to 2 Mbps), and
TIOCGICOUNT's frame/overrun/parity counters. Adds SCI0's pinout and
the new serial-test config to the EK-RA8M1 board page.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Assisted-by: Claude:claude-sonnet-5
Signed-off-by: leocafonso <leocafonso@gmail.com>
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