DynamicTablesPkg: AML Method parser

DynamicTablesPkg: AML Method parser

The AML language allows a Definition Block to implement
methods that an Operating System can invoke at runtime.

Although Dynamic AML does not provide interfaces to
modify AML methods; an AML template code may contain
methods and/or method invocations.

Method definitions have an opcode defined in the AML
encoding and can be easily parsed. However, the language
does not define an opcode for method invocation. Method
invocations are represented as a NameString followed by
the arguments to the method. This poses a significant
challenge for the AML parser as it has to determine if
a NameString appearing in the AML byte stream is a method
invocation and if it is a method invocation, then how
many arguments follow.

This also means the Method definition must occur prior to
the method invocation in the AML byte stream. This is a
hard requirement for the AML parser.

The AML method parser maintains a NameSpaceRefList that
keeps a track of every namespace node and its raw AML
absolute path. The AmlIsMethodInvocation() searches the
NameSpaceRefList to determine if a NameString matches
a Method definition.

A pseudo opcode has been defined in the AML encoding to
represent the Method invocation in the AML tree.

The AML encoding for method invocations in the ACPI
specification 6.3 is:
    MethodInvocation := NameString TermArgList

The AmlLib library redefines this as:
    MethodInvocation := MethodInvocationOp NameString
                          ArgumentCount TermArgList
    ArgumentCount    := ByteData

    Where MethodInvocationOp is the pseudo opcode and
    ArgumentCount is the number of arguments passed to
    the method.

NOTE:
  The AmlLib library's definition for a method
  invocation only applies to the representation
  of method invocation node in the AML tree.
  When computing the size of a tree or serialising
  it, the additional data is not taken into account
  i.e. the MethodInvocationOp and the ArgumentCount
  are stripped before serialising.

  Method invocation nodes have the AML_METHOD_INVOVATION
  attribute set in the AmlLib library's representation of
  the AML encoding.

Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>