dt-bindings: bus: Document moxtet bus binding

This adds device tree binding documentation for the Moxtet bus, a bus
via which the different modules connected to the Turris Mox router can
be configured.

Link: https://lore.kernel.org/r/20190812161118.21476-3-marek.behun@nic.cz
Signed-off-by: Marek Behún <marek.behun@nic.cz>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/Documentation/devicetree/bindings/bus/moxtet.txt b/Documentation/devicetree/bindings/bus/moxtet.txt
new file mode 100644 (file)
index 0000000..fb50fc8
--- /dev/null
+++ b/Documentation/devicetree/bindings/bus/moxtet.txt
@@ -0,0 +1,46 @@
+Turris Mox module status and configuration bus (over SPI)
+
+Required properties:
+ - compatible          : Should be "cznic,moxtet"
+ - #address-cells      : Has to be 1
+ - #size-cells         : Has to be 0
+ - spi-cpol            : Required inverted clock polarity
+ - spi-cpha            : Required shifted clock phase
+ - interrupts          : Must contain reference to the shared interrupt line
+ - interrupt-controller        : Required
+ - #interrupt-cells    : Has to be 1
+
+For other required and optional properties of SPI slave nodes please refer to
+../spi/spi-bus.txt.
+
+Required properties of subnodes:
+ - reg                 : Should be position on the Moxtet bus (how many Moxtet
+                         modules are between this module and CPU module, so
+                         either 0 or a positive integer)
+
+The driver finds the devices connected to the bus by itself, but it may be
+needed to reference some of them from other parts of the device tree. In that
+case the devices can be defined as subnodes of the moxtet node.
+
+Example:
+
+       moxtet@1 {
+               compatible = "cznic,moxtet";
+               #address-cells = <1>;
+               #size-cells = <0>;
+               reg = <1>;
+               spi-max-frequency = <10000000>;
+               spi-cpol;
+               spi-cpha;
+               interrupt-controller;
+               #interrupt-cells = <1>;
+               interrupt-parent = <&gpiosb>;
+               interrupts = <5 IRQ_TYPE_EDGE_FALLING>;
+
+               moxtet_sfp: gpio@0 {
+                       compatible = "cznic,moxtet-gpio";
+                       gpio-controller;
+                       #gpio-cells = <2>;
+                       reg = <0>;
+               }
+       };

diff --git a/MAINTAINERS b/MAINTAINERS
index 01309a2285934e3b5ecb06444fa6cab334216549..e0b803ba14186e0496b5298be6c83d32d05e720f 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1630,6 +1630,7 @@ ARM/CZ.NIC TURRIS MOX SUPPORT
 M:     Marek Behun <marek.behun@nic.cz>
 W:     http://mox.turris.cz
 S:     Maintained
+F:     Documentation/devicetree/bindings/bus/moxtet.txt
 F:     include/linux/moxtet.h
 F:     drivers/bus/moxtet.c