Add documentation for pm capabilties such as MMC_PM_KEEP_POWER
and MMC_PM_WAKE_SDIO_IRQ.
Signed-off-by: Abhilash Kesavan <a.kesavan@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
 - wp-inverted: when present, polarity on the wp gpio line is inverted
 - max-frequency: maximum operating clock frequency
 
+Optional SDIO properties:
+- keep-power-in-suspend: Preserves card power during a suspend/resume cycle
+- enable-sdio-wakeup: Enables wake up of host system on SDIO IRQ assertion
+
 Example:
 
 sdhci@ab000000 {
        cd-inverted;
        wp-gpios = <&gpio 70 0>;
        max-frequency = <50000000>;
+       keep-power-in-suspend;
+       enable-sdio-wakeup;
 }