ARM: bcm2835: Add names for the RPi Zero GPIO lines

This adds the GPIO names for the Raspberry Pi Zero. The GPIO lines
of the RPi Zero are almost identical to the Model A+ except:

* GPIO 35, 38, 40 and 45 are not connected
* Status LED is active low
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Eric Anholt <eric@anholt.net>

arch/arm/boot/dts/bcm2835-rpi-zero.dts

@@ -26,6 +26,71 @@ act {
 };
 
 &gpio {
+	/*
+	 * This is based on the official GPU firmware DT blob.
+	 *
+	 * Legend:
+	 * "NC" = not connected (no rail from the SoC)
+	 * "FOO" = GPIO line named "FOO" on the schematic
+	 * "FOO_N" = GPIO line named "FOO" on schematic, active low
+	 */
+	gpio-line-names = "SDA0",
+			  "SCL0",
+			  "SDA1",
+			  "SCL1",
+			  "GPIO_GCLK",
+			  "GPIO5",
+			  "GPIO6",
+			  "SPI_CE1_N",
+			  "SPI_CE0_N",
+			  "SPI_MISO",
+			  "SPI_MOSI",
+			  "SPI_SCLK",
+			  "GPIO12",
+			  "GPIO13",
+			  /* Serial port */
+			  "TXD0",
+			  "RXD0",
+			  "GPIO16",
+			  "GPIO17",
+			  "GPIO18",
+			  "GPIO19",
+			  "GPIO20",
+			  "GPIO21",
+			  "GPIO22",
+			  "GPIO23",
+			  "GPIO24",
+			  "GPIO25",
+			  "GPIO26",
+			  "GPIO27",
+			  "SDA0",
+			  "SCL0",
+			  "NC", /* GPIO30 */
+			  "NC", /* GPIO31 */
+			  "CAM_GPIO1", /* GPIO32 */
+			  "NC", /* GPIO33 */
+			  "NC", /* GPIO34 */
+			  "NC", /* GPIO35 */
+			  "NC", /* GPIO36 */
+			  "NC", /* GPIO37 */
+			  "NC", /* GPIO38 */
+			  "NC", /* GPIO39 */
+			  "NC", /* GPIO40 */
+			  "CAM_GPIO0", /* GPIO41 */
+			  "NC", /* GPIO42 */
+			  "NC", /* GPIO43 */
+			  "NC", /* GPIO44 */
+			  "NC", /* GPIO45 */
+			  "HDMI_HPD_N",
+			  "STATUS_LED_N",
+			  /* Used by SD Card */
+			  "SD_CLK_R",
+			  "SD_CMD_R",
+			  "SD_DATA0_R",
+			  "SD_DATA1_R",
+			  "SD_DATA2_R",
+			  "SD_DATA3_R";
+
 	pinctrl-0 = <&gpioout &alt0 &i2s_alt0>;
 
 	/* I2S interface */