Add a global binding for the chosen node.
Include a description of the stdout-path, and an explicit statement on
its extra options in the context of a UART console.
Opening description stolen from www.devicetree.org, and part of the
remaining text provided by Mark Rutland.
Signed-off-by: Leif Lindholm <leif.lindholm@xxxxxxxxxx>
---
Documentation/devicetree/bindings/chosen.txt | 42 ++++++++++++++++++++++++++
1 file changed, 42 insertions(+)
create mode 100644 Documentation/devicetree/bindings/chosen.txt
diff --git a/Documentation/devicetree/bindings/chosen.txt b/Documentation/devicetree/bindings/chosen.txt
new file mode 100644
index 0000000..9cd74e9
--- /dev/null
+++ b/Documentation/devicetree/bindings/chosen.txt
@@ -0,0 +1,42 @@
+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.
+
+
+stdout-path property
+--------------------
+
+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.
+
+/ {
+ chosen {
+ stdout-path = "/serial@f00:115200";
+ };
+
+ serial@f00 {
+ 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 format supported by uart_parse_options() is the
+expected one. In this case, the format of the string is:
+
+ <baud>{<parity>{<bits>{<flow>}}}
+
+where
+
+ baud - baud rate in decimal
+ parity - 'n' (none), 'o', (odd) or 'e' (even)
+ bits - number of data bits
+ flow - 'r' (rts)
+
+For example: 115200n8r
--
1.7.10.4
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