The Programmable Real-Time Unit - Industrial Communication
Subsystem (PRU-ICSS) is present on various TI SoCs such as
AM335x or AM437x or the Keystone 66AK2G. Each SoC can have
one or more PRUSS instances that may or may not be identical.
For example, AM335x SoCs have a single PRUSS, while AM437x has
two PRUSS instances PRUSS1 and PRUSS0, with the PRUSS0 being
a cut-down version of the PRUSS1.

The PRUSS consists of dual 32-bit RISC cores called the
Programmable Real-Time Units (PRUs), some shared, data and
instruction memories, some internal peripheral modules, and
an interrupt controller. The programmable nature of the PRUs
provide flexibility to implement custom peripheral interfaces,
fast real-time responses, or specialized data handling.

The PRU-ICSS functionality is achieved through three different
platform drivers addressing a specific portion of the PRUSS.
Some sub-modules of the PRU-ICSS IP reuse some of the existing
drivers (like davinci mdio driver or the generic syscon driver).
This design provides flexibility in representing the different
modules of PRUSS accordingly, and at the same time allowing the
PRUSS driver to add some instance specific configuration within
an SoC.

The PRUSS platform driver deals with the overall PRUSS and is
used for managing the subsystem level resources like various
memories and the CFG module. It is responsible for the creation
and deletion of the platform devices for the child PRU devices
and other child devices (like Interrupt Controller, MDIO node
and some syscon nodes) so that they can be managed by specific
platform drivers. The PRUSS interrupt controller is managed by
an irqchip driver, while the individual PRU RISC cores are
managed by a PRU remoteproc driver.

The driver currently supports the AM335x SoC, and support for
other TI SoCs will be added in subsequent patches.
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>