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The chosen node
The chosen node does not represent a real device, but serves as a place
for passing data between firmware and the operating system, like boot
arguments. Data in the chosen node does not represent the hardware.
Device trees may specify the device to be used for boot console output
with a stdout-path property under /chosen, as described in ePAPR, e.g.
stdout-path = "/serial@f00:115200";
compatible = "vendor,some-uart";
reg = <0xf00 0x10>;
If the character ":" is present in the value, this terminates the path.
The meaning of any characters following the ":" is device-specific, and
must be specified in the relevant binding documentation.
For UART devices, the preferred binding is a string in the form:
baud - baud rate in decimal
parity - 'n' (none), 'o', (odd) or 'e' (even)
bits - number of data bits
flow - 'r' (rts)
For example: 115200n8r
Implementation note: Linux will look for the property "linux,stdout-path" or
on PowerPC "stdout" if "stdout-path" is not found. However, the
"linux,stdout-path" and "stdout" properties are deprecated. New platforms
should only use the "stdout-path" property.
This property is set (currently only on PowerPC, and only needed on
book3e) by some versions of kexec-tools to tell the new kernel that it
is being booted by kexec, as the booting environment may differ (e.g.
a different secondary CPU release mechanism)