[U-Boot] [PATCH v2 12/12] dm: pci: Document binding of pci device drivers

[Bin Meng]

Document how pci devices are bound to device drivers.
Also mention its limitation in the pre-relocation phase.

Signed-off-by: Bin Meng <bmeng.cn at gmail.com>

---

Changes in v2: None

 doc/driver-model/pci-info.txt | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/doc/driver-model/pci-info.txt b/doc/driver-model/pci-info.txt
index cf69167..e016b98 100644
--- a/doc/driver-model/pci-info.txt
+++ b/doc/driver-model/pci-info.txt
@@ -34,9 +34,28 @@ under that bus.
 Note that this is all done on a lazy basis, as needed, so until something is
 touched on PCI (eg: a call to pci_find_devices()) it will not be probed.
 
-PCI devices can appear in the device tree. If they do this serves to specify
-the driver to use for the device. In this case they will be bound at
-start-up.
+PCI devices can appear in the flattened device tree. If they do this serves to
+specify the driver to use for the device. In this case they will be bound at
+first. Each PCI device node must have a compatible string list as defined by
+the IEEE Std 1275-1994 PCI bus binding document v2.1. An example like below:
+
+	pciuart0: uart at a,1 {
+		compatible = "pci8086,8811.00",
+			     "pci8086,8811",
+			     "pciclass,070002",
+			     "pciclass,0700",
+			     "x86-uart";
+	}
+
+Note the last string is the desired driver name which is supposed to work with
+this PCI device.
+
+If PCI devices are not listed in the device tree, U_BOOT_PCI_DEVICE can be used
+to specify the driver to use for the device. The device tree takes precedence
+over U_BOOT_PCI_DEVICE. Plese note with U_BOOT_PCI_DEVICE, only drivers with
+DM_FLAG_PRE_RELOC will be bound before relocation. If neither device tree nor
+U_BOOT_PCI_DEVICE is provided, the built-in driver (either pci_bridge_drv or
+pci_generic_drv) will be used.
 
 
 Sandbox
-- 
1.8.2.1