* Added some informations about the intervation_points.

docs/intervention_points

+For now using stable kernel v4.5.2
+
+######### GLOBAL:
+### How does Linux notice that there is a new device?
+This differs from device type to device type. For PCI Devices e.g. the kernel
+asks the pci interface driver for connected devices (see ???).
+The Kernel then generates a udev event.
+
+### How to make linux kernel load driver even when no hw is available?
+Linux kernel loads the module but how to make the kernel 'activating'
+this driver for not existing hardware? 
+TODO...
+
+#### How does Linux decide which driver to load for a new device?
+Kernel generates events (device uevents) with information abount device
+and udev searches for driver with matching PID/VID(product,vendor).
+Then udev loads the driver and creates device node.
+
+######### USB:
+### What abstraction layer can be used to supply virtual usb devices?
+For USB we need to create a interface where usb devices can be registered.
+There are three(?) possible places where this can be done.
+1.) Create driver for own USB Controller and ensure that this driver is executed.
+(By tricking the kernel into thinking there is a new controller?)
+
+2.) Create driver for own USB Hub and ensure that this driver is executed.
+(By tricking a usb controller into thinking there is a new device?) 
+
+3.) Trick usb controller into thinking that there is new device which redirects all the 
+calls from the usb driver to userspace.
+
+For all:
+TODO: How is connection between driver and usb device?
+
+### 1.) USB Controller:
+There are different USB Controller types:
+ohci = usb1.1
+uhci = usb1.x
+ehci = usb2.0
+xhci = usb1.x - usb3.0
+
+Because we want to be able to simulate different usb devices we use a XHCI controller because
+it has the ability to control all usb devices. 
+
+Drivers for usb controllers are in:
+drivers/usb/host/...
+e.g. drivers/usb/host/xhci-plat.c
+
+### 2.) USB Hubs: 
+Probably we could foist a virtual usb hub to one of the real usb controllers.
+
+TODO: Where does the Controller store his devices?
+TODO: Where are the drivers for usb hubs?
+
+### 3.) USB Devices
+
+TODO: Where does the Controller store his devices?
+TODO: How to redirect calls from driver?/ Where are driver calls going to?
+
+######### Other devices
+For other devices the only possibility is to use the 'top driver layer' (blockio/chario) 
+because underneath there is only the device driver which does direct hw access (in,out).
+
+We have to create a new module and register a own device driver with 
+int register_chrdev(unsigned int major, const char *name, struct file_operations *fops);
+int register_blkdev(unsigned int major, const char *name)
+
+TODO: How to let the kernel load this driver??
+
+# Character devices
+Only possible over the top character device layer (ioctl, read, write) [or by overriding in/out]
+
+# Block devices
+Only possible over the top block device layer (blockio) [or by overriding in/out]
+
+######### Network interface:
+TODO