docs: fix some broken references

[2] Devicetree NUMA binding description

    Documentation/devicetree/bindings/numa.txt

[3] RISC-V Linux kernel documentation

    Documentation/devicetree/bindings/riscv/cpus.txt

    Documentation/devicetree/bindings/riscv/cpus.yaml

[4] https://www.devicetree.org/specifications/

==========================================================

For a description of the TCU hardware and drivers, have a look at

Documentation/mips/ingenic-tcu.txt.

Documentation/mips/ingenic-tcu.rst.

Required properties:

  gpiochip. It will pass the struct gpio_chip* for the chip to all IRQ

  callbacks, so the callbacks need to embed the gpio_chip in its state

  container and obtain a pointer to the container using container_of().

  (See Documentation/driver-model/design-patterns.txt)

  (See Documentation/driver-api/driver-model/design-patterns.rst)

- gpiochip_irqchip_add_nested(): adds a nested cascaded irqchip to a gpiochip,

  as discussed above regarding different types of cascaded irqchips. The

-----------

This driver does not auto-detect devices. You will have to instantiate the

devices explicitly. Please see Documentation/i2c/instantiating-devices for

devices explicitly. Please see Documentation/i2c/instantiating-devices.rst for

details.

Sysfs entries

drivers access their registers through the same regmap.

For more information regarding the devicetree bindings of the TCU drivers,

have a look at Documentation/devicetree/bindings/mfd/ingenic,tcu.txt.

have a look at Documentation/devicetree/bindings/timer/ingenic,tcu.txt.