1 files changed, 52 insertions, 0 deletions

diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt
index 2aafda9254f0..528b4822f451 100644
--- a/Documentation/powerpc/booting-without-of.txt
+++ b/Documentation/powerpc/booting-without-of.txt
@@ -88,6 +88,10 @@ Table of Contents
     3) OpenPIC Interrupt Controllers
     4) ISA Interrupt Controllers
 
+  VIII - Specifying GPIO information for devices
+    1) gpios property
+    2) gpio-controller nodes
+
   Appendix A - Sample SOC node for MPC8540
 
 
@@ -3431,6 +3435,54 @@ encodings listed below:
         2 =  high to low edge sensitive type enabled
         3 =  low to high edge sensitive type enabled
 
+VIII - Specifying GPIO information for devices
+==============================================
+
+1) gpios property
+-----------------
+
+Nodes that makes use of GPIOs should define them using `gpios' property,
+format of which is: <&gpio-controller1-phandle gpio1-specifier
+                     &gpio-controller2-phandle gpio2-specifier
+                     0 /* holes are permitted, means no GPIO 3 */
+                     &gpio-controller4-phandle gpio4-specifier
+                     ...>;
+
+Note that gpio-specifier length is controller dependent.
+
+gpio-specifier may encode: bank, pin position inside the bank,
+whether pin is open-drain and whether pin is logically inverted.
+
+Example of the node using GPIOs:
+
+        node {
+                gpios = <&qe_pio_e 18 0>;
+        };
+
+In this example gpio-specifier is "18 0" and encodes GPIO pin number,
+and empty GPIO flags as accepted by the "qe_pio_e" gpio-controller.
+
+2) gpio-controller nodes
+------------------------
+
+Every GPIO controller node must have #gpio-cells property defined,
+this information will be used to translate gpio-specifiers.
+
+Example of two SOC GPIO banks defined as gpio-controller nodes:
+
+        qe_pio_a: gpio-controller@1400 {
+                #gpio-cells = <2>;
+                compatible = "fsl,qe-pario-bank-a", "fsl,qe-pario-bank";
+                reg = <0x1400 0x18>;
+                gpio-controller;
+        };
+
+        qe_pio_e: gpio-controller@1460 {
+                #gpio-cells = <2>;
+                compatible = "fsl,qe-pario-bank-e", "fsl,qe-pario-bank";
+                reg = <0x1460 0x18>;
+                gpio-controller;
+        };
 
 Appendix A - Sample SOC node for MPC8540
 ========================================